WIP 40x4 LCD: support in bios and emulator, minimal test rom, schematics

README.md

@@ -35,8 +35,8 @@ There is an experimental and unfinished quick load function using a python termi
 ![Pat80 Memory Monitor](/assets/media/photos/memory_monitor.jpg)
 
 ## Emulator
-The pat80 memory monitor (the os) can be run in a z80 emulator. This repository contains an emulator as submodule, already set up to run the os.
-To try it, head to `pat80-computer/software/z80-assembly/os/` and run `make run` to build the rom from assembly and start the emulator. You will see some windows showing the emulated computer's memory and register status and the pat80 memory monitor prompt.
+The pat80 memory monitor (the os) can be run in a z80 emulator. You can find a very simple one I wrote ad hoc in `pat80-emulator`. It's based (and depends on) the excellent [Z80 emulator library by redcode](https://github.com/redcode/Z80). Follow the instructions on `pat80-emulator/README.md` to build and run it.
+The emulator requires a rom file to run. To obtain a pat80 rom, head to `pat80-computer/software/z80-assembly/os/` and run `make run` to build the rom from assembly and start the emulator. You will see some windows showing the emulated computer's memory and register status and the pat80 memory monitor prompt.
 
 ![Emulator running Memory Monitor](/assets/media/photos/emulator.png)
 

pat80-computer/software/z80-assembly/os/Makefile

@@ -1,3 +1,5 @@
+PAT80_EMU_PATH := "../../../../pat80-emulator/build/pat80-emulator"
+
 build:
 	@echo "Building PAT80 rom..."
 	@z80asm -i main.asm -o rom.bin || (exit 1)
@@ -13,5 +15,9 @@ write: build
 	@minipro -w rom.bin -p "AT28C64B"
 
 run: build
-	@echo "Starting emulator..."
-	@../../../../pat80-emulator/z80-python-emulator/src/z80sbc.py -b rom.bin
+	@echo "Starting emulator" $(PAT80_EMU_PATH)
+	@if [ -f "$(PAT80_EMU_PATH)" ]; then\
+        "$(PAT80_EMU_PATH)" "rom.bin";\
+	else\
+		echo -e "\e[31mYou must build the emulator first. Check pat80-emulator/README.md\e[0m";\
+    fi

pat80-computer/software/z80-assembly/os/README.md

@@ -1,15 +1,24 @@
 # Pat80 Operating System and Memory Monitor
 
 ## Intro
+
 This folder contains the Pat80 Operating System.
 It is a System Monitor that makes available also some system API to access hardware (monitor, sound, keyboard, parallel terminal...).
 
 ## Build
+
 ### Requirements
-z80asm, minipro
+
+z80asm
+minipro (if you want to write to an EEPROM)
+
 ### Make
-The os can be build issuing command `make`.
+
+The os can be **built** issuing command `make build`.
 Two files will be generated:
 - `rom.bin` is the rom file to be flashed on the eeprom
 - `abi-generated.asm` is the file to be included in any Pat80 application to access system APIs (see README.md in ../applications/)
-The build routine will then try to write the rom to a MiniPRO.
+
+The os can be **written to an EEPROM** with a minipro-compatible programmer issuing command `make write`. This runs the build and then tries to write the rom to a MiniPRO.
+
+The os can otherwise be **runned in the emulator** issuing command `make run`. This requires to have the emulator executable already built (follow the instructions on `pat80-emulator/README.md` to build it).

pat80-computer/software/z80-assembly/os/drivers/TM404A_sn76489.asm

@@ -0,0 +1,102 @@
+; TM404A 40x4 characters LCD display (based on SN76489 chip) driver
+; @author Daniele Verducci
+; @language: Z80 ASM
+;
+;
+; This file is part of Pat80 Memory Monitor.
+;
+; Pat80 Memory Monitor is free software: you can redistribute it and/or modify
+; it under the terms of the GNU General Public License as published by
+; the Free Software Foundation, either version 3 of the License, or
+; (at your option) any later version.
+;
+; Pat80 Memory Monitor is distributed in the hope that it will be useful,
+; but WITHOUT ANY WARRANTY; without even the implied warranty of
+; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+; GNU General Public License for more details.
+;
+; You should have received a copy of the GNU General Public License
+; along with Pat80 Memory Monitor.  If not, see <http://www.gnu.org/licenses/>.
+;
+
+; --------------------------------------------------------------------------
+;
+; This is meant to be used with a 40x4 character display (containing a dual hd44780-compatible controller) like the TM404A.
+; This kind of display uses two controllers to overcome the hd44780 controllers limitation of 80 addressable characters.
+; It is seen as two separate displays, and thus have two EN pins. A finer implementation would apply some deconding logic to
+; an address bit to use a single port, but here we will use two different IO ports to save an IC.
+;
+; LCD config (IO port 0)
+LCD4004_TOP2LINES_PORT: EQU IO_2
+LCD4004_BOTTOM2LINES_PORT: EQU IO_3
+
+
+; PIN CONNECTIONS
+;
+; PIN   DESCRIPTION     TO PAT80 BUS PIN                INFO
+; ---------------------------------------------------------------------------------------------------
+; 1‐8   DB7‐DB0         DATA BUS
+; 9     E1 (chip en 1)  IOEN on LCD_TOP2LINES_PORT      Chip enable for top 2 lines
+; 10    R/W             IOWR
+; 11    RS              A4                              0: Command, 1: Data
+; 12 	V0 		        -	                            Power supply for contrast (approx. +0.5V)
+; 13 	Vss		        -	                            Ground
+; 14 	VDD 		    -	                            Power Supply Supply voltage for logic (+5.0V)
+; 15    E2 (chip en 2)  IOEN on LCD_BOTTOM2LINES_PORT   Chip enable for bottom 2 lines
+; 16 	NC 		        ‐ 	                            No Connect
+;
+
+
+; The 40x4 LCD memory map is the following:
+;
+; LINE      CHIP EN PIN     START ADDR      END ADDR
+; ----------------------------------------------------
+; 1         9               0x00 (0)        0x27 (39)
+; 2         9               0x40 (64)       0x67 (103)
+; 3         15              0x00 (0)        0x27 (39)
+; 4         15              0x40 (64)       0x67 (103)
+;
+; When we reach 0x40 on the first controller, we switch to the second.
+; When we reach 0x40 on the second controller, we must shift
+; all the lines up by one and position the cursor at 0x40.
+
+; variables
+LCD4004_VAR_SPACE: EQU DRV_IO_2_VAR_SPACE
+LCD4004_CURSOR_POSITION_CONTROLLER: EQU DRV_IO_2_VAR_SPACE  ; In which LCD controller is the cursor (0 or 1)
+LCD4004_CURSOR_POSITION_CONTROLLER_MEMORY: EQU DRV_IO_2_VAR_SPACE + 1   ; Memory position of the cursor inside the controller's memory
+
+; functions
+
+; Initializes the driver and the LCD screen
+LCD4004_Initialize:
+    ; The following are documented as in the datasheet: RS R/W DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0
+    ; Function set: 0 0 0 0 1 DL N F 0 0 (DL: 8-bit/4-bit, N: number of display lines 2/1, F: Font type 11dots/8dots)
+    ; 0000111000 (8 bit, 2 lines)
+    
+    ; Display ON/OFF Control: 0 0 0 0 0 0 1 D C B (D: display on/off, C: cursor on/off, B: blinking cursor on/off)
+    ; 0000001111 (display on, blinking cursor)
+    ; Clear display
+    ; 0000000001
+
+
+; Move cursor (set DDRAM address in address counter)
+LCD4004_MoveCursor:
+    ; 0 0 1 AC6 AC5 AC4 AC3 AC2 AC1 AC0 (ACx: Address)
+
+
+; Sends string
+; @param BC Pointer to a null-terminated string first character
+LCD4004_print:
+    ld a, (bc)  ; bc is the pointer to passed string's first char
+    cp 0        ; compare A content with 0 (subtract 0 from value and set zero flag Z if result is 0)
+    ret z       ; if prev compare is true (Z flag set), string is finished, return
+    out (TERM_DATA_REG),a    ; output char
+    inc bc ; increment bc to move to next char
+    jp LCD4004_print
+
+; Writes a single character
+; @param A Value of character to print
+LCD4004_printc:
+    out (TERM_DATA_REG),a
+    ret
+

pat80-computer/software/z80-assembly/os/drivers/arduino_terminal.asm

@@ -23,7 +23,7 @@ TERM_DATA_REG: EQU IO_0
 TERM_DATA_AVAIL_REG: EQU IO_0 + 1
 
 ; variables
-TERM_VAR_SPACE: EQU DRV_VAR_SPACE + 128
+TERM_VAR_SPACE: EQU DRV_IO_0_VAR_SPACE
 incoming_string: EQU TERM_VAR_SPACE
 
 ; functions

pat80-computer/software/z80-assembly/os/main.asm

@@ -30,8 +30,8 @@ jp Sysinit     ; Startup vector: DO NOT MOVE! Must be the first instruction
 ; I/O MAP
 ;   I/O 0 (0x00 - 0x1F) Parallel terminal (uses addr 0x00 and 0x01)
 ;   I/O 1 (0x20 - 0x3F) Sound card (uses addr 0x20 only)
-;   I/O 2 (0x40 - 0x5F) PS2 Keyboard (uses 0x40 and 0x41)
-;   I/O 3 (0x60 - 0x7F)
+;   I/O 2 (0x40 - 0x5F) 40x4 LCD, first controller (lines 1 and 2)
+;   I/O 3 (0x60 - 0x7F) 40x4 LCD, second controller (lines 3 and 4)
 ;   I/O 4 (0x80 - 0x9F)
 ;   I/O 5 (0xA0 - 0xBF)
 ;   I/O 6 (0xC0 - 0xDF)
@@ -89,12 +89,20 @@ Sys_Beep:
 
 
 ; MEMORY CONFIGURATION
-SYS_VAR_SPACE: EQU 0x8000
-DRV_VAR_SPACE: EQU 0x9000
-APP_SPACE: EQU 0xA000
+SYS_VAR_SPACE: EQU 0x8000   ; OS may allocate here memory for its own use
+DRV_VAR_SPACE: EQU 0x9000   ; IO devices drivers may allocate here memory, each has a chunk of 512 bytes
+DRV_IO_0_VAR_SPACE: EQU DRV_VAR_SPACE
+DRV_IO_1_VAR_SPACE: EQU DRV_IO_0_VAR_SPACE + 512
+DRV_IO_2_VAR_SPACE: EQU DRV_IO_1_VAR_SPACE + 512
+DRV_IO_3_VAR_SPACE: EQU DRV_IO_2_VAR_SPACE + 512
+DRV_IO_4_VAR_SPACE: EQU DRV_IO_3_VAR_SPACE + 512
+DRV_IO_5_VAR_SPACE: EQU DRV_IO_4_VAR_SPACE + 512
+DRV_IO_6_VAR_SPACE: EQU DRV_IO_5_VAR_SPACE + 512
+DRV_IO_7_VAR_SPACE: EQU DRV_IO_6_VAR_SPACE + 512
+APP_SPACE: EQU 0xA000   ; App may only allocate between there and MEM_END
 MEM_END: EQU 0xFFFF
 
-; SYSTEM CONFIGURATION
+; DEVICES ("cards" on the IO bus) I/O space
 IO_0: EQU 0x00
 IO_1: EQU 0x20
 IO_2: EQU 0x40
@@ -111,7 +119,7 @@ IO_7: EQU 0xE0
 
 ;include 'drivers/hd44780.asm'
 ;include 'drivers/keyboard.asm'
-include 'drivers/ps2_keyboard.asm'
+;include 'drivers/ps2_keyboard.asm'
 include 'drivers/arduino_terminal.asm'
 include 'drivers/sn76489.asm'
 include 'monitor.asm'

pat80-computer/software/z80-assembly/os/monitor.asm

@@ -25,7 +25,6 @@
 ;   S (SET) $pos $val Replaces byte at $pos with $val
 ;   L (LOAD) $pos $val
 ;   R (RUN) $pos Starts executing code from $pos
-;   A (ADB) Enters in Assembly Depoy Bridge mode: loads all the incoming bytes in application memory and starts executing.
 ; The commands are entered with a single letter and the program completes the command
 
 include 'libs/strings.asm'
@@ -38,13 +37,13 @@ MON_COMMAND_SET: DB "SET",0
 MON_COMMAND_ZERO: DB "ZERO",0
 MON_COMMAND_LOAD: DB "LOAD",0
 MON_COMMAND_RUN: DB "RUN",0
-MON_COMMAND_ADB: DB "ADB",0
 MON_COMMAND_MEMTEST: DB "MEMTEST",0
 MON_COMMAND_QUIT: DB "QUIT",0
 MON_ARG_HEX: DB "    0x",0
-MON_HELP: DB 10,"Available commands:\nHELP prints this message\nDUMP [ADDR] shows memory content\nSET [ADDR] sets memory content\nZERO [ADDR] [ADDR] sets all bytes to 0 in the specified range\nLOAD\nRUN [ADDR] executes code starting from ADDR\nADB starts Assembly Deploy Bridge\nMEMTEST checks ram boundaries\nQUIT exits",0
+MON_HELP: DB 10,"Available commands:\nHELP prints this message\nDUMP [ADDR] shows memory content\nSET [ADDR] sets memory content\nZERO [ADDR] [ADDR] sets all bytes to 0 in the specified range\nLOAD [ADDR] loads a program or data from tape at ADDR\nRUN [ADDR] executes code starting from ADDR\nADB starts Assembly Deploy Bridge\nMEMTEST checks ram boundaries\nQUIT exits",0
 MON_MSG_ADB: DB 10,"Waiting for data.",0
 MON_ERR_SYNTAX: DB "    Syntax error",0
+MON_COMMAND_LOAD_PRESSPLAY: DB "Press play on tape",0
 ; MON_RAMTEST_INTRO: DB " Checking memory... ",0
 ; MON_RAMTEST_RAMSTART: DB " Ram starts at 0x",0
 MON_DUMP_BYTES_LINES: EQU 8
@@ -84,9 +83,6 @@ Monitor_main:
         ld hl, MON_COMMAND_RUN
         cp (hl)
         jp z, monitor_run
-        ld hl, MON_COMMAND_ADB
-        cp (hl)
-        jp z, monitor_adb
         ; ld hl, MON_COMMAND_MEMTEST
         ; cp (hl)
         ; jp z, monitor_memtest
@@ -298,10 +294,18 @@ monitor_zero: ; TODO: bugged, doesn't exit cycle
 		ld (hl), 0 ; set byte to 0 in memory
 		ret
 
+
+; Asks user for a memory position, then wait for data from tape and place it
+; from the specified position on until it receives 4 consecutive 0x00 (EOF)
+; @uses b, c, h, l
 monitor_load:
     ld bc, MON_COMMAND_LOAD + 1 ; autocomplete command
     call Sys_Print
-	; TODO: When implemented, re-enable interrupts before run application
+	; Now read the memory address from the user
+    call monitor_arg_2byte  ; returns the read bytes in hl
+    ; Ask user to press play
+    ld bc, MON_COMMAND_LOAD_PRESSPLAY
+    ; TODO: wait for data
     jp monitor_main_loop
 
 monitor_run:
@@ -320,19 +324,6 @@ monitor_run:
 	; execute code
 	jp (hl)
 
-monitor_adb:
-    ld bc, MON_COMMAND_ADB + 1 ; autocomplete command
-    call Sys_Print
-    ; start copying incoming data to application space
-    call monitor_copyTermToAppMem
-	; call monitor_enable_int    ; re-enable interrupts
-    ;jp APP_SPACE    ; Start executing code
-
-
-    ; ld bc, APP_SPACE
-    ; call Sys_Print
-    jp monitor_main_loop
-
 ; Prints "0x" and read 1 hex byte (2 hex digits, e.g. 0x8C)
 ; Can be cancelled with Q/ENTER
 ; @return a the read byte, b the exit code (0=valid byte in a, 1=Q, 2=ENTER)
@@ -524,53 +515,6 @@ monitor_printAsciiByte:
     call Sys_Printc
     ret
 
-; Copy data from parallel terminal to application memory. This is tought to be used with the ADB function of the Pat80 Python Terminal.
-; Uses TERM_DATA_AVAIL_REG to check if a byte is available before reading it.
-; The first two received bytes (heading bytes) defines the stream length (MSB first), the rest of the bytes are copied to memory.
-; The copy is completed when the number of bytes defined in the heading bytes are received.
-; @uses a, b, c, d, h, l
-monitor_copyTermToAppMem:
-    ; d contains the current status.
-    ; 2 = waiting for first heading byte
-    ; 1 = waiting for second heading byte
-    ; 0 = heading bytes received, now receiving binary stream
-    ld d, 2
-    ld hl, APP_SPACE    ; we will write in APP_SPACE
-    monitor_copyTermToAppMem_loop:
-        ld a, d
-        cp 2    ; check if we are receiving first header byte
-        jp z, monitor_copyTermToAppMem_loop_rec_head_byte_1
-        ld a, d
-        cp 1    ; check if we are receiving second header byte
-        jp z, monitor_copyTermToAppMem_loop_rec_head_byte_2
-        ; we are receiving binary stream: read byte and save to memory
-        call Term_readb ; reads a byte from terminal
-        ld (hl), a  ; copy byte to memory
-        inc hl  ; move to next memory position
-        dec bc  ; decrement remaining bytes counter
-        ; check if we reached the number of bytes to be transferred
-        ld a, b
-        cp 0
-        jp nz, monitor_copyTermToAppMem_loop   ; continue loop
-        ld a, c
-        cp 0
-        jp nz, monitor_copyTermToAppMem_loop   ; continue loop
-        ; all bytes received, return
-        ret
-
-    monitor_copyTermToAppMem_loop_rec_head_byte_1:
-        ; we are receiving first header byte: read byte and save to b
-        call Term_readb ; reads a byte from terminal
-        ld b, a
-        dec d
-        jp monitor_copyTermToAppMem_loop   ; continue loop
-    monitor_copyTermToAppMem_loop_rec_head_byte_2:
-        ; we are receiving second header byte: read byte and save to c
-        call Term_readb ; reads a byte from terminal
-        ld c, a
-        dec d
-        jp monitor_copyTermToAppMem_loop   ; continue loop
-
 ; Runs a memory test to identify ram memory boundaries and check the ram is working.
 ; Starting from last memory position, writes 0xFF, reads it back, writes 0x00, reads it back.
 ; Exits when the first value differs from the written value (this may be caused by a bad ram

pat80-computer/software/z80-assembly/os/tests/TM404A.asm

@@ -0,0 +1,116 @@
+jp main     ; Startup vector: DO NOT MOVE! Must be the first instruction
+
+; Tests TM404A, on ports 2 and 3
+
+IO_2: EQU 0x40
+IO_3: EQU 0x60
+
+LCD_TOP_INSTR_REG: EQU IO_2
+LCD_TOP_DATA_REG: EQU IO_2 + 1
+LCD_BOTTOM_INSTR_REG: EQU IO_3
+LCD_BOTTOM_DATA_REG: EQU IO_3 + 1
+
+
+; Inits the lcd display
+LCD4004_init:
+    ; --- Init first controller ---
+
+    ; The following are documented as in the datasheet: RS R/W DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0
+    ; Function set: 0 0 0 0 1 DL N F 0 0 (DL: 8-bit/4-bit, N: number of display lines 2/1, F: Font type 11dots/8dots)
+    ; 0000111000 (8 bit, 2 lines)
+    ld a,0x38
+    out (LCD_TOP_INSTR_REG),a
+
+    call LCD4004_wait_busy_clear
+
+    ; Display ON/OFF Control: 0 0 0 0 0 0 1 D C B (D: display on/off, C: cursor on/off, B: blinking cursor on/off)
+    ; 0000001111 (display on, blinking cursor)
+    ld a,0x0F
+    out (LCD_TOP_INSTR_REG),a
+
+    call LCD4004_wait_busy_clear
+
+    ; Clear display
+    ; 0000000001
+    ld a,0x01
+    out (LCD_TOP_INSTR_REG),a
+
+    call LCD4004_wait_busy_clear
+
+    ; --- Init second controller ---
+
+    ; The following are documented as in the datasheet: RS R/W DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0
+    ; Function set: 0 0 0 0 1 DL N F 0 0 (DL: 8-bit/4-bit, N: number of display lines 2/1, F: Font type 11dots/8dots)
+    ; 0000111000 (8 bit, 2 lines)
+    ld a,0x38
+    out (LCD_BOTTOM_INSTR_REG),a
+
+    call LCD4004_wait_busy_clear
+
+    ; Display ON/OFF Control: 0 0 0 0 0 0 1 D C B (D: display on/off, C: cursor on/off, B: blinking cursor on/off)
+    ; 0000001111 (display on, blinking cursor)
+    ld a,0x0F
+    out (LCD_BOTTOM_INSTR_REG),a
+
+    call LCD4004_wait_busy_clear
+
+    ; Clear display
+    ; 0000000001
+    ld a,0x01
+    out (LCD_BOTTOM_INSTR_REG),a
+
+    call LCD4004_wait_busy_clear
+
+    ret
+
+
+; Prints string
+; @param BC Pointer to a null-terminated string first character
+LCD4004_TOP_print:
+    ld a, (bc)  ; bc is the pointer to passed string's first char
+    cp 0        ; compare A content with 0 (subtract 0 from value and set zero flag Z if result is 0)
+    ret z       ; if prev compare is true (Z flag set), string is finished, return
+    out (LCD_TOP_DATA_REG),a    ; output char
+    call LCD4004_wait_busy_clear     ; wait for the lcd to execute (busy signal check)
+    inc bc ; increment bc to move to next char
+    jp LCD4004_TOP_print
+
+; Prints string
+; @param BC Pointer to a null-terminated string first character
+LCD4004_BOTTOM_print:
+    ld a, (bc)  ; bc is the pointer to passed string's first char
+    cp 0        ; compare A content with 0 (subtract 0 from value and set zero flag Z if result is 0)
+    ret z       ; if prev compare is true (Z flag set), string is finished, return
+    out (LCD_BOTTOM_DATA_REG),a    ; output char
+    call LCD4004_wait_busy_clear     ; wait for the lcd to execute (busy signal check)
+    inc bc ; increment bc to move to next char
+    jp LCD4004_BOTTOM_print
+
+; Waits for the busy flag to be clear, indicating the LCD controllers to have finished their work
+LCD4004_wait_busy_clear:
+    ret
+    in a, (LCD_TOP_INSTR_REG)    ; reads the status
+    rla ; busy flag is DB7, so we shift it into carry to check it
+    jp c, LCD4004_wait_busy_clear ; if carry is set, lcd is busy
+    in a, (LCD_BOTTOM_INSTR_REG)    ; reads the status
+    rla ; busy flag is DB7, so we shift it into carry to check it
+    jp c, LCD4004_wait_busy_clear ; if carry is set, lcd is busy
+    ret
+
+; --- TEST CODE ---
+main:
+    TEST_STR_80: DB "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Etiam augue tortor sed.",0  ; null terminated string
+    TEST_STR_85: DB "2Lorem ipsum dolor sit amet, consectetur adipiscing elit praesent pellentesque nisi.",0  ; null terminated string
+
+    ; Init display
+    call LCD4004_init
+
+    ; Write string on first 2 lines
+    ld bc, TEST_STR_80
+    call LCD4004_TOP_print
+
+    ; Write long string on last 2 lines (to see how it wraps)
+    ld bc, TEST_STR_85
+    call LCD4004_BOTTOM_print
+
+    halt

pat80-emulator/README.md

@@ -1,5 +1,7 @@
 # Pat80 emulator
 
+![Emulator running Memory Monitor](/assets/media/photos/emulator.png)
+
 ## Setup
 
 Install the required Z80 emulator by redcode following the instructions for your Linux distribution at https://github.com/redcode/Z80

pat80-emulator/main.c

@@ -2,6 +2,7 @@
  * PAT80 Emulator
  *
  * Emulates a PAT80.
+ * Based on https://github.com/redcode/Z80
  */
 
 #include <Z/constants/pointer.h> /* Z_NULL */
@@ -29,6 +30,8 @@ typedef struct {
         Z80     cpu;
         WINDOW  *terminal_win;
         WINDOW  *status_win;
+        WINDOW  *lcd_top_win;   // 40x4 LCD, top two lines
+        WINDOW  *lcd_bottom_win;   // 40x4 LCD, bottom two lines
 } Machine;
 
 
@@ -49,8 +52,8 @@ static zuint8 machine_cpu_in(Machine *self, zuint16 port) {
         // so the 3 most significant IO addr bits in this case are A7, A6, A5. The bits
         // A4-A0 may be used by the single device, at its own discretion.
         zuint16 bitmask = 7; // 0000000000000111
-        int decoded = port & bitmask;
-	if (decoded <= 0x1F) {
+        int ioDevice = port & bitmask;
+	if (ioDevice <= 0x1F) {
 		// Port 0 (0x00 to 0x1F): terminal
 		// Read char from stin
                 char c = getch();
@@ -65,37 +68,45 @@ static zuint8 machine_cpu_in(Machine *self, zuint16 port) {
                                 return c;
                 }
         }
-        if (decoded <=  0x3F) {
+        if (ioDevice <=  0x3F) {
                 // Port 1 (0x20 to 0x3F): sound card (sn76489)
 		wprintw(self->status_win, "sound_cmd[IN]: Not supported!\n");
                 return 0x00;
         }
-        if (decoded <=  0x5F) {
-                // Port 2 (0x40 to 0x5F)
+        if (ioDevice <=  0x5F) {
+                // Port 2 (0x40 to 0x5F): LCD top 2 lines
+                if (port == 0x40 || port == 0x60) {
+                        // TODO: Simulate busy flag and cursor position
+                        return 0x00;    // Busy flag clear, for now
+                }
                 wprintw(self->status_win, "IO_ERROR_IN: No device at port 2\n");
                 return 0x00;
         }
-        if (decoded <=  0x7F) {
-                // Port 3 (0x60 to 0x7F)
+        if (ioDevice <=  0x7F) {
+                // Port 3 (0x60 to 0x7F): LCD bottom 2 lines
+                if (port == 0x0) {
+                        // TODO: Simulate busy flag and cursor position
+                        return 0x00;
+                }
                 wprintw(self->status_win, "IO_ERROR_IN: No device at port 3\n");
                 return 0x00;
         }
-        if (decoded <=  0x9F) {
+        if (ioDevice <=  0x9F) {
                 // Port 4 (0x80 to 0x9F)
                 wprintw(self->status_win, "IO_ERROR_IN: No device at port 4\n");
                 return 0x00;
         }
-        if (decoded <=  0x5F) {
+        if (ioDevice <=  0x5F) {
                 // Port 5 (0xA0 to 0xBF)
                 wprintw(self->status_win, "IO_ERROR_IN: No device at port 5\n");
                 return 0x00;
         }
-        if (decoded <=  0x5F) {
+        if (ioDevice <=  0x5F) {
                 // Port 6 (0xC0 to 0xDF)
                 wprintw(self->status_win, "IO_ERROR_IN: No device at port 6\n");
                 return 0x00;
         }
-        if (decoded <=  0x5F) {
+        if (ioDevice <=  0x5F) {
                 // Port 7 (0xE0 to 0xFF)
                 wprintw(self->status_win, "IO_ERROR_IN: No device at port 7\n");
         } else {
@@ -106,6 +117,8 @@ static zuint8 machine_cpu_in(Machine *self, zuint16 port) {
         refresh();
         wrefresh(self->terminal_win);
         wrefresh(self->status_win);
+        wrefresh(self->lcd_top_win);
+        wrefresh(self->lcd_bottom_win);
 }
 
 
@@ -115,29 +128,56 @@ static void machine_cpu_out(Machine *self, zuint16 port, zuint8 value) {
         // so the 3 most significant IO addr bits in this case are A7, A6, A5. The bits
         // A4-A0 may be used by the single device, at its own discretion.
         zuint16 bitmask = 0xE0; // 0000000011100000
-        int decoded = port & bitmask;
-	if (decoded <= 0x1F) {
+        int ioDevice = port & bitmask;
+        bitmask = 0x1F; // 0000000000011111
+        int ioAddrInsideDevice = port & bitmask;
+        wprintw(self->status_win, "[%#06x]DECODED[%#04x] - ", port, ioDevice);
+	if (ioDevice <= 0x1F) {
 		// Port 0 (0x00 to 0x1F): terminal
 		wprintw(self->terminal_win, "%c", value);
-	} else if (decoded <= 0x3F) {
+	} else if (ioDevice <= 0x3F) {
                 // Port 1 (0x20 to 0x3F): sound card (sn76489)
 		wprintw(self->status_win, "sound_cmd[%#04x]\n", value);
-        } else if (decoded <= 0x5F) {
-                // Port 2 (0x40 to 0x5F)
-                wprintw(self->status_win, "IO_ERROR_OUT: No device at port 2\n");
-        } else if (decoded <= 0x7F) {
-                // Port 3 (0x60 to 0x7F)
-                wprintw(self->status_win, "IO_ERROR_OUT: No device at port 3\n");
-        } else if (decoded <= 0x9F) {
+        } else if (ioDevice <= 0x5F) {
+                // Port 2 (0x40 to 0x5F) and Port 3 (0x60 to 0x7F):
+                // lcd display 40x4 (mod. TM404A, based on 2 KS0066 chips, each one controlling 2 rows,
+                // top controller at port 2 and bottom at port 3).
+                // Instruction register at each port first address, data register at second address
+                if (ioAddrInsideDevice == 0) {
+                        // Port 2, A4 LOW = talking to LCD top 2 lines instruction register
+		        wprintw(self->status_win, "lcd_top_cmd[%#04x]\n", value);
+                } else if (ioAddrInsideDevice == 1) {
+                        // Port 2, A4 HIGH = talking to LCD top 2 lines data register (writing text to screen)
+                        wprintw(self->status_win, "lcd_top_data[%#04x](%c)\n", value, value);
+                        wprintw(self->lcd_top_win, "%c", value);
+                } else {
+                        wprintw(self->status_win, "IO_ERROR_OUT: lcd (top controller) does not listen at addr %#04x\n", ioAddrInsideDevice);
+                }
+        } else if (ioDevice <= 0x7F) {
+                // Port 2 (0x40 to 0x5F) and Port 3 (0x60 to 0x7F):
+                // lcd display 40x4 (mod. TM404A, based on 2 KS0066 chips, each one controlling 2 rows,
+                // top controller at port 2 and bottom at port 3).
+                // Instruction register at each port first address, data register at second address
+                if (ioAddrInsideDevice == 0) {
+                        // Port 3, A4 LOW = talking to LCD bottom 2 lines instruction register
+		        wprintw(self->status_win, "lcd_bottom_cmd[%#04x]\n", value);
+                } else if (ioAddrInsideDevice == 1) {
+                        // Port 3, A4 HIGH = talking to LCD bottom 2 lines data register (writing text to screen)
+                        wprintw(self->status_win, "lcd_bottom_data[%#04x](%c)\n", value, value);
+                        wprintw(self->lcd_bottom_win, "%c", value);
+                } else {
+                        wprintw(self->status_win, "IO_ERROR_OUT: lcd (bottom controller) does not listen at addr %#04x\n", ioAddrInsideDevice);
+                }
+        } else if (ioDevice <= 0x9F) {
                 // Port 4 (0x80 to 0x9F)
                 wprintw(self->status_win, "IO_ERROR_OUT: No device at port 4\n");
-        } else if (decoded <= 0x5F) {
+        } else if (ioDevice <= 0xBF) {
                 // Port 5 (0xA0 to 0xBF)
                 wprintw(self->status_win, "IO_ERROR_OUT: No device at port 5\n");
-        } else if (decoded <= 0x5F) {
+        } else if (ioDevice <= 0xDF) {
                 // Port 6 (0xC0 to 0xDF)
                 wprintw(self->status_win, "IO_ERROR_OUT: No device at port 6\n");
-        } else if (decoded <= 0x5F) {
+        } else if (ioDevice <= 0xFF) {
                 // Port 7 (0xE0 to 0xFF)
                 wprintw(self->status_win, "IO_ERROR_OUT: No device at port 7\n");
         } else {
@@ -148,6 +188,21 @@ static void machine_cpu_out(Machine *self, zuint16 port, zuint8 value) {
         refresh();
         wrefresh(self->terminal_win);
         wrefresh(self->status_win);
+        wrefresh(self->lcd_top_win);
+        wrefresh(self->lcd_bottom_win);
+}
+
+static void machine_cpu_halt(Machine *self, unsigned char signal) {
+        wprintw(self->status_win, "HALTED (%d)\n", signal);
+        // Refresh all windows
+        refresh();
+        wrefresh(self->terminal_win);
+        wrefresh(self->status_win);
+        wrefresh(self->lcd_top_win);
+        wrefresh(self->lcd_bottom_win);
+        // Wait an ESC before exiting
+        while (getch() != 27) {}
+        exit(0);
 }
 
 
@@ -160,7 +215,7 @@ void machine_initialize(Machine *self) {
         self->cpu.write        = (Z80Write)machine_cpu_write;
         self->cpu.in           = (Z80Read )machine_cpu_in;
         self->cpu.out          = (Z80Write)machine_cpu_out;
-        self->cpu.halt         = Z_NULL;
+        self->cpu.halt         = (Z80Halt)machine_cpu_halt;
         self->cpu.nmia         = Z_NULL;
         self->cpu.inta         = Z_NULL;
         self->cpu.int_fetch    = Z_NULL;
@@ -210,6 +265,7 @@ int main(int argc, char *argv[]) {
         start_color();                  // Use colors
         init_pair(1, COLOR_WHITE, COLOR_BLUE); // Terminal window color
         init_pair(2, COLOR_YELLOW, COLOR_BLACK); // Status window color
+        init_pair(3, COLOR_BLACK, COLOR_GREEN); // LCD window color
         int x,y;
         getmaxyx(stdscr, y,x);
 
@@ -219,13 +275,19 @@ int main(int argc, char *argv[]) {
                 /*zusize*/  .cycles = 0,
                 /*Z80*/     .cpu = pat80Cpu,
                 .terminal_win = newwin(TERMINAL_HEIGHT, TERMINAL_WIDTH, INSTRUCTION_WINDOW_HEIGHT, 0),
-                .status_win = newwin(y, x - TERMINAL_WIDTH - SPACING_BETWEEN_WINDOWS, INSTRUCTION_WINDOW_HEIGHT, TERMINAL_WIDTH + SPACING_BETWEEN_WINDOWS)
+                .status_win = newwin(y, x - TERMINAL_WIDTH - SPACING_BETWEEN_WINDOWS, INSTRUCTION_WINDOW_HEIGHT, TERMINAL_WIDTH + SPACING_BETWEEN_WINDOWS), // To right of terminal window
+                .lcd_top_win = newwin(2, 40, INSTRUCTION_WINDOW_HEIGHT + TERMINAL_HEIGHT + SPACING_BETWEEN_WINDOWS, 0),  // Below terminal window
+                .lcd_bottom_win = newwin(2, 40, INSTRUCTION_WINDOW_HEIGHT + TERMINAL_HEIGHT + SPACING_BETWEEN_WINDOWS + 2, 0)
         };
 
         wbkgd(pat80.terminal_win, COLOR_PAIR(1));       // Ncurses: set terminal window color
         wbkgd(pat80.status_win, COLOR_PAIR(2));
+        wbkgd(pat80.lcd_top_win, COLOR_PAIR(3));
+        wbkgd(pat80.lcd_bottom_win, COLOR_PAIR(3));
         scrollok(pat80.terminal_win, TRUE);             // Ncurses: Allow scrolling when reached end of window
         scrollok(pat80.status_win, TRUE);
+        scrollok(pat80.lcd_top_win, FALSE);
+        scrollok(pat80.lcd_bottom_win, FALSE);
         attron(A_BOLD);                                 // Print instructions
         printw("Emulator commands\n");
         attroff(A_BOLD);
@@ -251,6 +313,8 @@ int main(int argc, char *argv[]) {
         // Stop ncurses
         delwin(pat80.terminal_win);
         delwin(pat80.status_win);
+        delwin(pat80.lcd_top_win);
+        delwin(pat80.lcd_bottom_win);
         endwin();
         return 0;
 }

pat80-io-devices/4004 lcd display/hardware/4004_lcd_display/4004_lcd_display.kicad_pcb

@@ -0,0 +1,2 @@
+(kicad_pcb (version 20240108) (generator "pcbnew") (generator_version "8.0")
+)

pat80-io-devices/4004 lcd display/hardware/4004_lcd_display/4004_lcd_display.kicad_prl

@@ -0,0 +1,83 @@
+{
+  "board": {
+    "active_layer": 0,
+    "active_layer_preset": "",
+    "auto_track_width": true,
+    "hidden_netclasses": [],
+    "hidden_nets": [],
+    "high_contrast_mode": 0,
+    "net_color_mode": 1,
+    "opacity": {
+      "images": 0.6,
+      "pads": 1.0,
+      "tracks": 1.0,
+      "vias": 1.0,
+      "zones": 0.6
+    },
+    "selection_filter": {
+      "dimensions": true,
+      "footprints": true,
+      "graphics": true,
+      "keepouts": true,
+      "lockedItems": false,
+      "otherItems": true,
+      "pads": true,
+      "text": true,
+      "tracks": true,
+      "vias": true,
+      "zones": true
+    },
+    "visible_items": [
+      0,
+      1,
+      2,
+      3,
+      4,
+      5,
+      8,
+      9,
+      10,
+      11,
+      12,
+      13,
+      15,
+      16,
+      17,
+      18,
+      19,
+      20,
+      21,
+      22,
+      23,
+      24,
+      25,
+      26,
+      27,
+      28,
+      29,
+      30,
+      32,
+      33,
+      34,
+      35,
+      36,
+      39,
+      40
+    ],
+    "visible_layers": "fffffff_ffffffff",
+    "zone_display_mode": 0
+  },
+  "git": {
+    "repo_password": "",
+    "repo_type": "",
+    "repo_username": "",
+    "ssh_key": ""
+  },
+  "meta": {
+    "filename": "4004_lcd_display.kicad_prl",
+    "version": 3
+  },
+  "project": {
+    "files": []
+  }
+}

pat80-io-devices/4004 lcd display/hardware/4004_lcd_display/4004_lcd_display.kicad_pro

@@ -0,0 +1,392 @@
+{
+  "board": {
+    "3dviewports": [],
+    "design_settings": {
+      "defaults": {},
+      "diff_pair_dimensions": [],
+      "drc_exclusions": [],
+      "rules": {},
+      "track_widths": [],
+      "via_dimensions": []
+    },
+    "ipc2581": {
+      "dist": "",
+      "distpn": "",
+      "internal_id": "",
+      "mfg": "",
+      "mpn": ""
+    },
+    "layer_presets": [],
+    "viewports": []
+  },
+  "boards": [],
+  "cvpcb": {
+    "equivalence_files": []
+  },
+  "erc": {
+    "erc_exclusions": [],
+    "meta": {
+      "version": 0
+    },
+    "pin_map": [
+      [
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        1,
+        0,
+        0,
+        0,
+        0,
+        2
+      ],
+      [
+        0,
+        2,
+        0,
+        1,
+        0,
+        0,
+        1,
+        0,
+        2,
+        2,
+        2,
+        2
+      ],
+      [
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        1,
+        0,
+        1,
+        0,
+        1,
+        2
+      ],
+      [
+        0,
+        1,
+        0,
+        0,
+        0,
+        0,
+        1,
+        1,
+        2,
+        1,
+        1,
+        2
+      ],
+      [
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        1,
+        0,
+        0,
+        0,
+        0,
+        2
+      ],
+      [
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        0,
+        2
+      ],
+      [
+        1,
+        1,
+        1,
+        1,
+        1,
+        0,
+        1,
+        1,
+        1,
+        1,
+        1,
+        2
+      ],
+      [
+        0,
+        0,
+        0,
+        1,
+        0,
+        0,
+        1,
+        0,
+        0,
+        0,
+        0,
+        2
+      ],
+      [
+        0,
+        2,
+        1,
+        2,
+        0,
+        0,
+        1,
+        0,
+        2,
+        2,
+        2,
+        2
+      ],
+      [
+        0,
+        2,
+        0,
+        1,
+        0,
+        0,
+        1,
+        0,
+        2,
+        0,
+        0,
+        2
+      ],
+      [
+        0,
+        2,
+        1,
+        1,
+        0,
+        0,
+        1,
+        0,
+        2,
+        0,
+        0,
+        2
+      ],
+      [
+        2,
+        2,
+        2,
+        2,
+        2,
+        2,
+        2,
+        2,
+        2,
+        2,
+        2,
+        2
+      ]
+    ],
+    "rule_severities": {
+      "bus_definition_conflict": "error",
+      "bus_entry_needed": "error",
+      "bus_to_bus_conflict": "error",
+      "bus_to_net_conflict": "error",
+      "conflicting_netclasses": "error",
+      "different_unit_footprint": "error",
+      "different_unit_net": "error",
+      "duplicate_reference": "error",
+      "duplicate_sheet_names": "error",
+      "endpoint_off_grid": "warning",
+      "extra_units": "error",
+      "global_label_dangling": "warning",
+      "hier_label_mismatch": "error",
+      "label_dangling": "error",
+      "lib_symbol_issues": "warning",
+      "missing_bidi_pin": "warning",
+      "missing_input_pin": "warning",
+      "missing_power_pin": "error",
+      "missing_unit": "warning",
+      "multiple_net_names": "warning",
+      "net_not_bus_member": "warning",
+      "no_connect_connected": "warning",
+      "no_connect_dangling": "warning",
+      "pin_not_connected": "error",
+      "pin_not_driven": "error",
+      "pin_to_pin": "warning",
+      "power_pin_not_driven": "error",
+      "similar_labels": "warning",
+      "simulation_model_issue": "ignore",
+      "unannotated": "error",
+      "unit_value_mismatch": "error",
+      "unresolved_variable": "error",
+      "wire_dangling": "error"
+    }
+  },
+  "libraries": {
+    "pinned_footprint_libs": [],
+    "pinned_symbol_libs": []
+  },
+  "meta": {
+    "filename": "4004_lcd_display.kicad_pro",
+    "version": 1
+  },
+  "net_settings": {
+    "classes": [
+      {
+        "bus_width": 12,
+        "clearance": 0.2,
+        "diff_pair_gap": 0.25,
+        "diff_pair_via_gap": 0.25,
+        "diff_pair_width": 0.2,
+        "line_style": 0,
+        "microvia_diameter": 0.3,
+        "microvia_drill": 0.1,
+        "name": "Default",
+        "pcb_color": "rgba(0, 0, 0, 0.000)",
+        "schematic_color": "rgba(0, 0, 0, 0.000)",
+        "track_width": 0.2,
+        "via_diameter": 0.6,
+        "via_drill": 0.3,
+        "wire_width": 6
+      }
+    ],
+    "meta": {
+      "version": 3
+    },
+    "net_colors": null,
+    "netclass_assignments": null,
+    "netclass_patterns": []
+  },
+  "pcbnew": {
+    "last_paths": {
+      "gencad": "",
+      "idf": "",
+      "netlist": "",
+      "plot": "",
+      "pos_files": "",
+      "specctra_dsn": "",
+      "step": "",
+      "svg": "",
+      "vrml": ""
+    },
+    "page_layout_descr_file": ""
+  },
+  "schematic": {
+    "annotate_start_num": 0,
+    "bom_export_filename": "",
+    "bom_fmt_presets": [],
+    "bom_fmt_settings": {
+      "field_delimiter": ",",
+      "keep_line_breaks": false,
+      "keep_tabs": false,
+      "name": "CSV",
+      "ref_delimiter": ",",
+      "ref_range_delimiter": "",
+      "string_delimiter": "\""
+    },
+    "bom_presets": [],
+    "bom_settings": {
+      "exclude_dnp": false,
+      "fields_ordered": [
+        {
+          "group_by": false,
+          "label": "Reference",
+          "name": "Reference",
+          "show": true
+        },
+        {
+          "group_by": true,
+          "label": "Value",
+          "name": "Value",
+          "show": true
+        },
+        {
+          "group_by": false,
+          "label": "Datasheet",
+          "name": "Datasheet",
+          "show": true
+        },
+        {
+          "group_by": false,
+          "label": "Footprint",
+          "name": "Footprint",
+          "show": true
+        },
+        {
+          "group_by": false,
+          "label": "Qty",
+          "name": "${QUANTITY}",
+          "show": true
+        },
+        {
+          "group_by": true,
+          "label": "DNP",
+          "name": "${DNP}",
+          "show": true
+        }
+      ],
+      "filter_string": "",
+      "group_symbols": true,
+      "name": "Grouped By Value",
+      "sort_asc": true,
+      "sort_field": "Riferimento"
+    },
+    "connection_grid_size": 50.0,
+    "drawing": {
+      "dashed_lines_dash_length_ratio": 12.0,
+      "dashed_lines_gap_length_ratio": 3.0,
+      "default_line_thickness": 6.0,
+      "default_text_size": 50.0,
+      "field_names": [],
+      "intersheets_ref_own_page": false,
+      "intersheets_ref_prefix": "",
+      "intersheets_ref_short": false,
+      "intersheets_ref_show": false,
+      "intersheets_ref_suffix": "",
+      "junction_size_choice": 3,
+      "label_size_ratio": 0.375,
+      "operating_point_overlay_i_precision": 3,
+      "operating_point_overlay_i_range": "~A",
+      "operating_point_overlay_v_precision": 3,
+      "operating_point_overlay_v_range": "~V",
+      "overbar_offset_ratio": 1.23,
+      "pin_symbol_size": 25.0,
+      "text_offset_ratio": 0.15
+    },
+    "legacy_lib_dir": "",
+    "legacy_lib_list": [],
+    "meta": {
+      "version": 1
+    },
+    "net_format_name": "",
+    "page_layout_descr_file": "",
+    "plot_directory": "",
+    "spice_current_sheet_as_root": false,
+    "spice_external_command": "spice \"%I\"",
+    "spice_model_current_sheet_as_root": true,
+    "spice_save_all_currents": false,
+    "spice_save_all_dissipations": false,
+    "spice_save_all_voltages": false,
+    "subpart_first_id": 65,
+    "subpart_id_separator": 0
+  },
+  "sheets": [
+    [
+      "b60673c4-5448-4b81-8c25-50d47b52f4a5",
+      "Root"
+    ]
+  ],
+  "text_variables": {}
+}