One of the SITCOM training computer prototypes
 SITCOM 85 Training Computer
 
  In order to make a training computer such as Sitcom work in an efficient and useful manner, it must incorporate facilities by which single or multiple program steps may be changed with an absolute minimum of fuss and effort. This is normally achieved by giving the training computer its own simple operating system, namely a Ďmonitor programí which means that a totally anonymous program is running in the background all the time. Whilst this can work well after a fashion, it is a long way from writing a program that runs in the microprocessors memory area on its own with no operating system routines to either avoid or possibly interfere with it. Izabella's recommended programming order
 
  Sitcom memory management Sitcom does not use this method, instead using a minimal sized Boot Prom whose programming automatically loads a program down the simple serial link into the RAM. Once downloaded, the user simply presses the RESET button to tell the glue logic to substitute the RAM into the bottom 32K of the memory area where the ROM just was! This way the program runs as if it were programmed in a PROM from location 0000h.
 
  PROGRAMMING SITCOM
 
  Another plug for San's SB Assembler Thus we arrive at the reason you are building Sitcom - to learn how to program a microprocessor! In order to do this on the assumption your Sitcom is now working correctly, you will need to set up your PC computer with a suitable Assembler program. As Iíve said before, you are welcome to continue using the one you already have (if you have previous programming experience that is), however, you might like to try Sanís SB-Assembler anyway, as you will almost certainly be able to use it straight away, and it does of course contain special features and short cuts over other Assemblers that you will soon appreciate I am sure.
 
  If you are using the SB-Assembler there are a few simple instructions to include at the head of your programs if you are intending to download them to a Sitcom, as shown below:
 
 

        .CR     8085           Sets up the 8085 cross assembler
        .CP     1,9600,N,8,1   Comms options, 9600 baud no parity, 8 bits 1 stop
        .TF     COM1:,INT      Send target file to COM1 in Intel Hex Format
 
These three lines must appear in the head of every Sitcom program when using the SB-Assembler
 
  Please note that these lines assume you are using COM1 and a crystal of 6.000MHz or 6.144MHz. This will be true for all the programs you'll find on this site.
If you are using a different COM port on your PC you'll have to change 2 values in the header. The first '1' on the CP line is the COM port number, and obviously the COM1: parameter of the third line directs the output to COM1.
If you're using a 3.000MHz or 3.072MHz crystal in your Sitcom you must change the baud rate at line 2 to 4800.
 
  As there is nothing better than seeing an actual example of a Sitcom program written in the SB-Assembler, have a look at the example below:
 
   

;---------------------------------------------------------------
;
;  This simple program tests the operation of the SITCOM85
;  It displays an arbitrary 8 character word on the 2 displays
;
;  SITCOM is to be connected to COM1: or else you should change
;  the lines containing the .CP and .TF directives.
;
;---------------------------------------------------------------
         .CR   8085
         .CP   1,9600,N,8,1
         .TF   COM1:,INT

;---------------------------------------------------------------

IZABELLA MVI   A,'I'            Say Izabella
         OUT   0C3H
         MVI   A,'Z'
         OUT   0C2H
         MVI   A,'A'
         OUT   0C1H
         MVI   A,'B'
         OUT   0C0H
         MVI   A,'E'
         OUT   0E3H
         MVI   A,'L'
         OUT   0E2H
         MVI   A,'L'
         OUT   0E1H
         MVI   A,'A'
         OUT   0E0H

.4EVER   JMP   .4EVER          Endless loop

;---------------------------------------------------------------

         .LI   OFF
     
san.asm
 
  If you have a Sitcom with one or two DL1414 displays, you may like to try this program. Simply copy the source file and paste it in your text editor, then save it as 'san.asm' for instance. Then you can assemble the program by giving the command 'sbasm san' on a DOS prompt.
 
  GOTO Programs page 2 - Assembler VS Machine Code. Another real example
 
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