Hi, I am trying to write a program to display custom character on LCD using CGRAM. I am using 68HC11 MCU and 20x2 LCD for this purpose. I attached my code in attachment. I don't seem to get anything on LCD. The HEX pattern, CC, is supposed to look like a speaker. Any help would great. Code: ORG $6000 CC FCB $06,$0f,$0f,$0f,$0f,$0f,$0f,$00 ORG $7000 MAIN JSR LCD_CLR JSR DSP_CC SWI DSP_CC LDY #$40 JSR LCD_TEST LDX #CC JSR LCD_DSP RTS LCD_CLR LDAA #$01 JSR LCD_TEST STAA $1400 RTS LCD_TEST TST $1400 BMI LCD_TEST RTS LCD_DSP LDAA 0,X LDAB 0,Y STAB $1400 CMPA #00 BEQ FINISH JSR LCD_TEST STAA $1401 INX INY JMP LCD_DSP FINISH RTS
How does Code: 00000110 00001111 00001111 00001111 00001111 00001111 00001111 look like a speaker? How does the MCU know to start executing the program at $7000? I'm not a 68HC11 expert but I've done a bit of PIC programming and you need to put a jump at the start of program memory if that's not where the start of the program is. Obviously ignore this if the 68HC11 starts at $7000. LDAA 0,X - OK, I guess this reads the 06 ff ff etc since X is initialised to #CC. LDAB 0,Y - So what does this do? Y is initialised to #$40.
I am sorry that is definitely not speaker look alike. It is supposed to look like a battery. But the my it doesn't make difference to the problem. Answering your question one at a time. Once the program is loaded. Using a BUFFALO monitor program I would type go 7000 to run the program, Where 7000 is a hex and address from where my main subroutine starts. Your second question, LDAB #$40, is the instruction that will initialize CGRAM. $40 corresponds to first row of 5x8 pixel map. So, $40~$47 for 8 rows. Last row is 00 for cursor. I am newbie but I have some assembly and now trying to play around. I tried following the instruction in the website below but its for different MCU. w w w.8051projects.net/lcd-interfacing/lcd-custom-character.php
> Your second question, LDAB #$40, is the instruction that will initialize CGRAM. $40 corresponds to first row of 5x8 pixel map. So, $40~$47 for 8 rows. Last row is 00 for cursor. Um, sorry I'm being thick. Where's the instruction that writes to $40~47?
Hmm its alright. You see first Index Register Y is initialized to $40. Then it is incremented using INY. It is also stored in $1400 LCD Control Register, which tells the address in CGRAM to right hex pattern.
