Thursday, April 24, 2014

68k project: step 7 - CP/M 68, booting from Srecords

Ok, lets start from code. Code for ChVII
  The firmware is mostly [or exactly?] the same, but there are two new directories - BIOS ,which contains BIOS (sort of ugly bios), and Disk, which contains pretty empty disk image and diskdefs for cpmtools. (local)
The disk image itself contains A: - P: drives, cpmtools with this diskdefs are able to write to A: . Write there a whole CP/M distribution. The disk image comes from Searle Grant's Z80 SBC, (or even my mentioned SD interface for it) as all the DPB stuff.
  For the bios reassembly use assemble script, you'll get bios.s. Next, load it and CPM15000.SR via cut-and-paste to SBC console.
  Personally I do it with kermit. It's much better for our use then saying minicom.
  Here is my kermit initialization (I hope I forgot nothing:)
set line /dev/ttyS0
set car off
set speed 38400
set flow rts
set transmit timeout 10

(and set input echo on, but I forgot what it is for and if it is really needed)    So from SBC prompt say
* boot
, it will initialise the card and load something ($2000 bytes?) to somewhere ($1000?). But currently we do not care.
  Next, load bios.s and CPM15000.SR by

 C-Kermit> transmit CPM15000.SR


 C-Kermit> transmit bios.s

Next, run it via go15000 and get A:.
  The next thing is to create CPMLDR and CPM.SYS. Sure, we will create them on the board. But I refuse to learn CP/M ed!
So, the next thing I going to do is to get some text editor. And that will be separate chapter or two.

Some things to mention:
  • First, get .68K files from .REL . That's done by series of RELOCX.SUB scripts
  • if AS68 says can't open 0:AS68SYMB.DAT, ensure you have AS68INIT from DISK3 and run AS68 -I AS68INIT for every TPA change
  • A very good article how to recalculate DPBs into cpmtools diskdefs.
    It does not help me much because it is long and clever; I always guess some things (and probably wrong)

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