[vcf-midatlantic] Mystery ROM from MITS 88-PMC ROM Board

[Systems Glitch]

Mike Douglas caught my goof -- it is the DBL ROM. The image I have, that I *thought* was the DBL ROM, was actually a Tarbell single-density boot ROM!

Thanks,
Jonathan

On Fri, 29 Jan 2016 16:05:25 -0500
Herb Johnson via vcf-midatlantic <vcf-midatlantic at lists.vintagecomputerfederation.org> wrote:

>  > It starts with LXI SP, 0xFF13 -- a ROM location. I've seen
>  > the trick used elsewhere, to reduce code size by using
>  > an in-ROM jump table. Anyone recognize the code?
> 
> 
> ORG 0FF00H
> 
> LXI H, 0FF13H
> LXI D, 2C00H
> MVI C, 0EBH
> L1: MOV A,M
> STAX D
> INX H
> INX D
> DCR C
> JNZ L1	;0FF08H
> JMP 2C00H
> 
> ;above moves code from ROM to RAM and executes
> 
> ORG 2C00H; but code follows ROM code above at FF13H
> 
> DI
> XRA A
> OUT 22H
> CMA
> OUT 23H
> MVI A, 2CH
> OUT 22H
> MVI A, 03H
> OUT 19H
> IN 0FFH
> ANI 10H
> RRC
> RRC
> ADI 10H
> OUT 10H
> LXI SP, 2D79H
> XRA A
> 
> ; next byte is at FF30H in ROM
> ; further disassembly should be instructive
> 
> 
> -- 
> Herbert R. Johnson,  New Jersey USA
> http://www.retrotechnology.com OR .net
>