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Since version mios_v1_5b MIOS has supported 4-bit mode for HD44780 compatible displays

Usually this mode isn't needed, but some displays have been internally configured for 4-bit operation and don't have all the necessary connections for full 8-bit operation or You might have some other reason to try this mode out.

To configure MIOS application to use 4-bit CLCD mode, changes need to be made to the application:

First locate
'USER_Init' section of the source files 1)

Then add to its own section just below the 'USER_Init' 2):

;; use a CLCD, E input of first CLCD at D.7, E of second CLCD @C.4

     ;; using the 4-bit interface:
     ;; -> connect MBHP_CORE:J15:D7-D4 of the core module to D7-D4 of the LCD
     ;; -> left MBHP_CORE:J15:D3-D0 of the core module open!
     ;; -> tie D3-D0 of the LCD to ground
     movlw   0x37 | 0x80     ; E1: D.7, 4bit interface
     movwf   MIOS_PARAMETER1
     movlw   0x24 | 0x80     ; E2: C.4, 4bit interface
     movwf   MIOS_PARAMETER2
     movlw   0x00            ; LCD type 0
     call    MIOS_LCD_TypeSet''

Then you have to Compile the modified application.

See the comments 3) in the code for how to connect the display to the core. In the display side, having the datasheet for it helps a lot.

More: MIOS function reference

usually in 'main.asm', in MB_SID ''
Don't add it in between the initialization commands or you can break something this way
marked with ;; in the beginning of the line
dictionary/4-bit_mode.txt · Last modified: 2007/11/17 17:18 (external edit)