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