notANON

Even this slow old architecture is actually still really quick.  You’ll often need to burn off some clock cycles between operations just so you can see the output.  Here is a little subroutine I wrote for the 1802 that is adjustable and can be shoehorned into code you may have already written.  You can hook it write into many of the early programs in Tom Pittman’s book “A Short Course in Programming“.  Pretty much anything that has you pushing the “I” key for it to move forward.

0020    F81F    LDI The second byte determines the delay amount

0022    B4        PHI R4 Puts the delay counter into R4

0023    32XX   BZ XX Branch if D=0, second byte directs back.

0025    94        GHI R4 Puts the counter from R4 into D for comparison

0026    24        DEC R4 Decrements R4 by one

0027    3020   BR XX Branches back to check if D is zero.

Here is an example where I have hooked the delay back into my hex counter program so that you don’t have to push “I” for the counter to increment.  I have left the old code structure in tact so you can see the differences.  I also changed the counter location in memory to 0030 but this is arbitrary.

TinyELF Hex autocounter

0000   6400  OUT 4    clear hex display
0002   90       GHI R0  zero the accumulator
0003   B2       PHI R2   Set hi byte to zero
0004   B3       PHI R3   Set hi byte to zero
0005   A3       PLO R3  Set lo byte to zero
0006   F830  LDI         Set D to 30
0008   A2      PLO R2  Set R2 to 30
0009 52         STR Clear 0030 byte
000A   E2      SEX R2  Set X to R2
000B   3020 BR           Instead of waiting for “I”, branch to delay
000D   13       INC R3  Count up
000E   83      GLO R3  Set D to the current count
000F   52       STR R2   Store counter value in 0030
0010   64        OUT 4     Put contents of 0030 on display
0011   22        DEC R2  Keep X pointing at 0030
0012   C4C4   NOP        No need to wait for “i” to be lifted now
0014   300B   BR           Loop back to where wait for “I” was

timer routine;
0020   F85F LDI         The second byte determines the delay amount
0022   B4      PHI R4  Puts the delay counter into R4
0023   320D BZ          Branch when D=0 back to AFTER the branch to 0020
0024   94      GHI R4  Puts the counter from R4 into D for comparison
0025   24      DEC R4  Decrements R4 by one
0027   3023 BR           Branches back to check if D is zero.