Table of Pointers

[Chris Roper]

I am trying to create a table of pointers to functions but this test code is not working.

No errors are generated, it compiles and flashes fine, but does nothing.
Am I attempting the impossile or do I have a syntax error ?

' table test

#chip 18F25K50

dim fnadr as word
dir portb out

Do
  for index = 1 to 4
    ReadTable test, index, fnadr
    IndCall fnadr
    wait 250 ms
  next
Loop

END

sub setled1()
    portb   = 0
    portb.0 = 1
end sub

sub setled2()
    portb   = 0
    portb.1 = 1
end sub

sub setled3()
    portb   = 0
    portb.2 = 1
end sub

sub setled4()
    portb   = 0
    portb.3 = 1
end sub

table test as Word
  @setled1
  @setled2
  @setled3
  @setled4
end table

I am testing with the Microchip 28 pin demo board.
Ultimately I need two tables of 255 entries each, the above is just a simplified test of concept.

Any advice and help would be appreciated.

Chrees
Chris

[Chris Roper]

I have made some progress:

By adding:

setled1 : wait 250 ms
setled2 : wait 250 ms
setled3 : wait 250 ms
setled4 : wait 250 ms

Between the 'dir portb out' and the 'do' lines the program runs.

I would say that the table of pointers is not being populated becouse the functions are not compiled unless specificaly called.

However the 'wait' statement is needed for some reason
Just having:

setled1
setled2
setled3
setled4

fails the same as the first test code

What am I missing?

Cheers
Chris

EDIT:
Another test, changing the wait to 100 ms implies that the setup code is looping, dispite being out side of the loop. Eventualy it stops entierly, my guess is that the table is still not being populated correctly and that the Processor is resetting when it enters the loop.

[Anobium]

You do not think you can have pointers in tables as you are defining them.

Data tables can be define by (in Great Cow Basic v0.95 or greater - you will be able to use items 1, 2 and 3 in earlier versions).
1. a single value on each line
2. multiple elements on a single line separated by commas
3. constants and calculations within the single line data table entries are permitted
4. an external data source file

The table is not being created beyond the four byte length of the table.

So, the question is. What are you trying to achieve ? I am sure we have other methods to achieve the goal you are looking require.

[Chris Roper]

I am using the v0.94 build and have tried with both multypal eliment single line and the version shown above.

I was reading item 3 to imply that I could use the @function style as a calculation/constant.

Here is what I am trying to achive:

Given a Byte lookup and execute the two functions assosiated with fetching the argument and executing the opperation on the argument.

It is a CPU emulation for educational use and the lookup tables would change between CPU types.

table opcode2fnAdr as Word ' return pointer to opcode execution subroutine
' 0  |  1  |  2  |  3  |  4  |  5  |  6  |  7  |  8  |  9  |  A  |  B  |  C  |  D  |  E  |  F  ;
      @ora, @nop, @slo, @nop, @ora, @asl, @slo, @php, @ora, @asl, @nop, @nop, @ora, @asl, @slo,; 0
@bpl, @ora, @nop, @slo, @nop, @ora, @asl, @slo, @clc, @ora, @nop, @slo, @nop, @ora, @asl, @slo,; 1
@jsr, @amd, @nop, @rla, @b1t, @amd, @rol, @rla, @plp, @amd, @rol, @nop, @b1t, @amd, @rol, @rla,; 2
@bmi, @amd, @nop, @rla, @nop, @amd, @rol, @rla, @sec, @amd, @nop, @rla, @nop, @amd, @rol, @rla ; 3
@rti, @eor, @nop, @sre, @nop, @eor, @lsr, @sre, @pha, @eor, @lsr, @nop, @jmp, @eor, @lsr, @sre ; 4
@rti, @eor, @nop, @sre, @nop, @eor, @lsr, @sre, @pha, @eor, @lsr, @nop, @jmp, @eor, @lsr, @sre ; 5
@rts, @adc, @nop, @rra, @nop, @adc, @ror, @rra, @pla, @adc, @ror, @nop, @jmp, @adc, @ror, @rra ; 6
@bvs, @adc, @nop, @rra, @nop, @adc, @ror, @rra, @sei, @adc, @nop, @rra, @nop, @adc, @ror, @rra ; 7
@nop, @sta, @nop, @sax, @sty, @sta, @stx, @sax, @dey, @nop, @txa, @nop, @sty, @sta, @stx, @sax ; 8
@bcc, @sta, @nop, @nop, @sty, @sta, @stx, @sax, @tya, @sta, @txs, @nop, @nop, @sta, @nop, @nop ; 9
@ldy, @lda, @ldx, @lax, @ldy, @lda, @ldx, @lax, @tay, @lda, @tax, @nop, @ldy, @lda, @ldx, @lax ; A
@bcs, @lda, @nop, @lax, @ldy, @lda, @ldx, @lax, @clv, @lda, @tsx, @lax, @ldy, @lda, @ldx, @lax ; B
@cpy, @cmp, @nop, @dcp, @cpy, @cmp, @dec, @dcp, @iny, @cmp, @dex, @nop, @cpy, @cmp, @dec, @dcp ; C
@bne, @cmp, @nop, @dcp, @nop, @cmp, @dec, @dcp, @cld, @cmp, @nop, @dcp, @nop, @cmp, @dec, @dcp ; D
@cpx, @sbc, @nop, @isb, @cpx, @sbc, @inc, @isb, @inx, @sbc, @nop, @sbc, @cpx, @sbc, @inc, @isb ; E
@beq, @sbc, @nop, @isb, @nop, @sbc, @inc, @isb, @sed, @sbc, @nop, @isb, @nop, @sbc, @inc, @isb ; F
end table

table opcode2AdMod as Word ' return pointer to addressing mode subroutine
' 0  |  1  |  2  |  3  |  4  |  5  |  6  |  7  |  8  |  9  |  A  |  B  |  C  |  D  |  E  |  F  ;
      @idx, @imp, @idx, @zpg, @zpg, @zpg, @zpg, @imp, @imm, @acc, @imm, @aba, @aba, @aba, @aba ; 0
@rel, @dxy, @imp, @dxy, @zpx, @zpx, @zpx, @zpx, @imp, @aby, @imp, @aby, @abx, @abx, @abx, @abx ; 1
@abo, @idx, @imp, @idx, @zpg, @zpg, @zpg, @zpg, @imp, @imm, @acc, @imm, @abo, @abo, @abo, @abo ; 2
@rel, @idy, @imp, @idy, @zpx, @zpx, @zpx, @zpx, @imp, @aby, @imp, @aby, @abx, @abx, @abx, @abx ; 3
@imp, @idx, @imp, @idx, @zpg, @zpg, @zpg, @zpg, @imp, @imm, @acc, @imm, @abo, @abo, @abo, @abo ; 4
@rel, @idy, @imp, @idy, @zpx, @zpx, @zpx, @zpx, @imp, @aby, @imp, @aby, @abx, @abx, @abx, @abx ; 5
@imp, @idx, @imp, @idx, @zpg, @zpg, @zpg, @zpg, @imp, @imm, @acc, @imm, @ind, @abo, @abo, @abo ; 6
@rel, @idy, @imp, @idy, @zpx, @zpx, @zpx, @zpx, @imp, @aby, @imp, @aby, @abx, @abx, @abx, @abx ; 7
@imm, @idx, @imm, @idx, @zpg, @zpg, @zpg, @zpg, @imp, @imm, @imp, @imm, @abo, @abo, @abo, @abo ; 8
@rel, @idy, @imp, @idy, @zpx, @zpx, @zpy, @zpy, @imp, @aby, @imp, @aby, @abx, @abx, @aby, @aby ; 9
@imm, @idx, @imm, @idx, @zpg, @zpg, @zpg, @zpg, @imp, @imm, @imp, @imm, @abo, @abo, @abo, @abo ; A
@rel, @idy, @imp, @idy, @zpx, @zpx, @zpy, @zpy, @imp, @aby, @imp, @aby, @abx, @abx, @aby, @aby ; B
@imm, @idx, @imm, @idx, @zpg, @zpg, @zpg, @zpg, @imp, @imm, @imp, @imm, @abo, @abo, @abo, @abo ; C
@rel, @dxy, @imp, @dxy, @zpx, @zpx, @zpx, @zpx, @imp, @aby, @imp, @aby, @abx, @abx, @abx, @abx ; D
@imm, @idx, @imm, @idx, @zpg, @zpg, @zpg, @zpg, @imp, @imm, @imp, @imm, @abo, @abo, @abo, @abo ; E
@rel, @dxy, @imp, @dxy, @zpx, @zpx, @zpx, @zpx, @imp, @aby, @imp, @aby, @abx, @abx, @abx, @abx ; F
end table

' Fetch Decode and Execute opcode

exeopcode(PC)

dim AdMod as word
dim FnAdr as word
dim opArg as word

sub exeopcode(adr as word)
   ' Obtain Operation Argument
  ReadTable opcode2AdMod, opcode, AdMod
  IndCall AdMod
  ' Execute Operation
  ReadTable opcode2FnAdr, opcode, FnAdr
  IndCall FnAdr
end sub

To attempt that dual lookup with a Select Case or If Then statements would be too slow and verbose.

Cheers
Chris

[Anobium]

Thank you - this helps me understand.

Leave this for a day or two and check back. But, you may be able to use one of the new features of v0.95 of Great Cow Basic to do this. Need to talk to Hugh to get his view.

Please hold in there.

[Chris Roper]

Thanks Evan,

Much appreciated
Cheers
Chris