; 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