Unable to locate SWR on a Watford Electronic ROM/RAM board

[rjpontefract]

I tried running beeb-step on my Model B with a Watford Electronics ROM/RAM board which has one 16K static RAM at slot E and 128K of DRAM providing SWR in slots 0 through 7. As it stands the beeb-step demo can't locate enough SWR to run as it needs 4 slots and fails to locate any of the SWR in slots 0 through 7.

I made a couple of modifications to swr.asm to make it work.

In the loop where it scans for SWR I add the following to program the latch used by the WE board:

    ; scan for roms
    ldx #15
.rom_loop
    stx &f4:stx &fe30   ; select rom bank
    sta &ff30,x         ; Watford ROM/RAM board 
    ldy #0      ; assume rom
    lda &8008   ; read byte

and in .swr_select_slot and .swr_select_bank:

    sta &f4
    tax                 ; Watford ROM/RAM board
    sta &ff30,x         ; Watford ROM/RAM board
    sta swr_slot_selected

    sta &fe30
    tax                 ; Watford ROM/RAM board
    sta &ff30,x         ; Watford ROM/RAM board
;    cli

That enables it (and presumably any other BitShifters demo that uses swr.asm) to work with the WE board.

Hope that helps someone.