indirect address help

[engenharia23]

Posted on July 07, 2009 at 12:59

indirect address help

[engenharia23]

Posted on May 17, 2011 at 15:03

Hi all!

My name is Fabio Fortes, I have found very difficult to write a code in assembler for stm8s105k4. I am working with the IDE STVD, and would appreciate some help, I believe, simple ... I am working on a routine lcd, and must have access to so indirectly, using the x register, however, I have not managed to write the code. could someone help me? grateful, fabio :-?

[fggnrc]

Posted on May 17, 2011 at 15:03

Hello Fabio.

LCD control may be an easy or a difficult task according to the driving method. On this site there are some examples which show how a microcontroller can generate the waveforms to directly drive the electrodes (a difficult task). I however suppose that you have to accomplish an easier task, i.e. to drive a LCD controller such as a HD44780. If such is the case, you have to: - link the microcontroller with the LCD controller; - send the right command sequence. If you need some help, please, give more details since they make the difference when it's time to write any assembler code. Regards EtaPhi

[engenharia23]

Posted on May 17, 2011 at 15:03

Hello, thank you very much for your attention!

I already work in assembler codes with st7foxk1 and lcd. I usualy reserve 32 bytes of ram to data lcd. for to send data to ram, with st7, I use: ;************************************************************* ;SUB-ROTINE to clean the LCD clean: LD A,#020H ; set a ... LD RPOS,A ; ... counter LD X,#RLCD ; first address of lcd ram in X LD A,#020H ; acc = ' ' VOLT2: LD (X),A ; (X) = acc INC X ; DEC RPOS ; dec counter JRNE VOLT2 ; RET ; RETURN ;************************************************************* this code working very well with st7foxk1, but, when I try to load X in stm8s, I receive the message: Error 54: Can't match Addressing mode ' LD X,#RLCD' So, I would like to know, what I need to do to work with indirect address in stm8s. I'm trying to work with stm8s105k4. Grateful, Fábio Fortes, Caxias do Sul, Rio Grande do Sul, Brazil.

[fggnrc]

Posted on May 17, 2011 at 15:03

Fabio,

I had your same error when I moved from the ST7 to the STM8S core... The X register is now 16 bits wide, so the instruction to load the X register with the RLCD constant is LDW X,#RLCD As a rule of thumb, all instructions that involve X or Y have now to be followed by a ''W''. 8 bit data can be still exchanged between X and A, but you have to say which half is involved. This means that you have to write LD A,XL to transfer the lower byte of X to A. The STM8S core and its 16 bit index registers are a big evolution of the ST7 assembler programming model: what you did (or you was forced to do) is now not necessary because there are new efficient ways to achieve the same result. For instance, you can set a variable initial value with: MOV RLCD,#$1E The corresponding ST7 assembler instructions are: LD A,#$1E LD RLCD,A but they need 6 (if the destination is in the zero page) or 7 clock cycles instead of one clock cycle! Regards, EtaPhi