Epson PX-8 : dumping 6303 rom

[mk2s]

With a program like:
10 CLEAR, &H9900:BDOS=&H9900
20 FOR I=0 TO 40:READ XOKE BDOS+I,X:NEXT
25 OPEN "o",#1,"px86303a.txt"
30 FOR I=0 TO 255
40 PRINT IRINT #1,HEX$(&HF000+I*16);":";
50 H=((&HF000+I*16)AND &HFF00)\256
60 IF H<0 THEN H=H+256
80 POKE &H9925,H
90 FOR J=0 TO 15
100 POKE &H9926, (I*16+J) MOD 256
110 CALL BDOS
120 IF PEEK(&H9927)<>0 THEN ERROR 21
130 PRINT #1,HEX$(PEEK(&H9928));" ";
140 NEXT J
150 PRINT #1,:NEXT I
155 CLOSE #1
160 DATA &h3e, &hc0, &h32, &h58, &hf3, &h21, &h14, &h99
170 DATA &he5, &h2a, &h01, &h00, &h11, &h72, &h00, &h19
180 DATA &h11, &h1c, &h99, &he9, &h4f, &h3e, &h00, &h32
190 DATA &h58, &hf3, &h79, &hc9, &h24, &h99, &h03, &h00
200 DATA &h27, &h99, &h02, &h00, &h00, &hf0, &h02, &h00
210 DATA &h00

I was able to get the following out of my US px-8.

For those interested the data statements are:
0000 ; code snippet to read a byte from slave space
9900 .ORG 9900h
9900 3E C0 LD a,0c0h
9902 32 58 F3 LD (0f358h),a
9905 21 14 99 LD hl,retaddr
9908 E5 PUSH hl
9909 2A 01 00 LD hl,(1)
990C 11 72 00 LD de,72H ; bios slave command
990F 19 ADD hl,de
9910 11 1C 99 LD de,packet
9913 E9 JP (hl)
9914 4F RETADDR: LD c,a
9915 3E 00 LD a,0
9917 32 58 F3 LD (0f358h),a
991A 79 LD a,c
991B C9 RET
991C 24 99 PACKET: DW sendsv
991E 03 00 DW 3
9920 27 99 DW rcvsv
9922 02 00 DW 2
9924 00 SENDSV: DB 0 ; read
9925 F0 DB 0f0h ; hi
9926 00 DB 00h ; lo
9927 00 RCVSV: DB 0
9928 00 DB 0

I make no guarantees that this is correct, but it's a starting point. I wanted to look at it with Ghidra and then realized that it doesn't do the 6303 too well.

....maki....

 

[fjkraan]

Isn't the 6303 just a clone of the 6803, which is a subset of the 6801 configurations? Ghidra, or any 6801 disassembler should make something reasonable from the code. The attached file is created with f6dasm (https://github.com/Arakula/f9dasm). Apart from the first part, at first glance, it looks like reasonable 6801 code.
Fred Jan

 

[mk2s]

sort of tangentially related to this topic PocketGriffon has a HC-88 and he has analyzed the 6303 rom and written a blog post about it here(that I just found and read): https://pocketgriffon.hatenablog.com/entry/2020/10/25/004914
I recently paid for a HC-88 and so expect to have one in hand in the new year. I'll share some photos. The HC-88 was a variant of the PX-8 with Japanese language support. Most of the differences were in the software and the expansion unit(which was included when you bought the 88) The expansion unit was non-intelligent 64k ramdisk plus kanji ROM. The keyboard and the ROMs on the main board were different.