HC11 LCD Display problem

Sep 15, 2003 5 Replies
P

Gurus,



I am a virgin and need some help here. I want to display the content of a location on the LCD Display. Please have a look at the code and help me. With the current progra the problem is that it displays correctly the value at the first



2 postions of the display, but after these positions there is junk displayed.

Below is the relevant code. IT is for an HC11



Thanks Peter



LDA #$01 ;CLEAR AND HOME BSR WCTRL ;WRITE CONTROL BYTE TO LCD LDA #%11111111 ; load something.. in this case the display should show FF JSR BIN2ASC ; convert bin2ascii STD 0,X BSR LCDTEXT ; show it SWI ; break here for now


***************************************************
  • SEND A LINE OF TEXT TO LCD
  • PASS START ADDRESS OF TEXT IN X
  • TEXT STRING TERMINATED BY * SEND A LINE OF TEXT TO LCD
    *     PASS START ADDRESS OF TEXT IN X
    * TEXT STRING TERMINATED BY $00 OR $04 OR

*************************************************** LCDTEXT PSHA LCD LDAA 0,X ;GET BYTE FROM MESSAGE TABLE CMPA #$00 ;Check for end of string BEQ DLCD ;$00 OR $04 CMPA #$04 BEQ DLCD BSR WDAT ;SEND CHARACTER TO LCD INX BRA LCD DLCD PULA RTS


********************************************



******* BIN TO ASCII ************
********************************************
*Converts 8 bit binary value in ACCA to ACII
*PASSED : Binary value in ACCA
*RETURNS: ASCII in D
*EFFECTS: ACCB is destroyed
******************************************** HEX_TABLE FCC "0123456789ABCDEF" ; Table for conversion values

BIN2ASC PSHA ; Save a copy of the input number on the stack TAB ; Copy into ACCB ANDB #%00001111 ; Strip the upper nibble of ACCB CLRA ; D now contains 000n where n is the LS nibble ADDD #HEX_TABLE ; setup for indexed load XGDX LDA 0,X ; GEt the LSnibble Character PULB ; retrieve the input number into ACCB PSHA ; put the LSNIBBLE into place RORB ; Move the upper nipple into of the input number RORB ; into the llower position RORB RORB ANDB #%00001111 ; strip off the upper nipple CLRA ; D now contains 000n where n is the msnibble ADDD #HEX_TABLE XGDX LDAA 0,X ; Get the MSnibble character in ACCA PULB ; retrieve the LSnibble character into ACCB RTS


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G

I don't see how any of that works towards solving the first problem you mentioned. In fact it's likely to worsen it.

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G

I take that back, the eleventh line from the end of your listing may help somewhat.

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P

Thanks for your real helpful advise.

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G

Lighten up, it was funny. Maybe.

Anyway in the third line it looks like you're only loading one byte into your message table, and never setting a stop character ($00 or $04) at all! So the first two letters which will be "FF" will display fine, but when the loop comes around to load more characters or detect a stop character, you've set nothing. Therefore the program will spit out whatever happens to be in that memory location and won't quit until it finds a $00 or $04.

At least that's my feeble, never-having-used-an-HC11-myself opinion.

Hope that helps.

(hee hee, don't forget to strip that upper, uh, "nibble")

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P

Hey that was helpful. Thanks for the advise.

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