I pointed you at the BIOS docs first, since the S-100 system is
quite a bit different from the ECB board suite. Compatibility at
the BIOS level would simplify the implementation of CP/M-68, since
16-bit (S-100) CP/M is going to be the same as 8-bit (baby ECB)
I would expect the underlying S-100 BIOS to be significantly different from the ECB M68k BIOS, since the underlying I/O hardware is totally different.
The SBC-188 BIOS project proceeded rather briskly, as we had the IBM PC BIOS interface as our target.
A single BIOS interface, perhaps using the baby M68K BIOS docs as a starting point, might allow the two projects to take advantage of one another.
I am only familiar with CP/M on the Z80, where the "BIOS" level is implemented by calls through a vector table. That is effectively what the baby M68k BIOS is doing. All function call numbers are purely arbitrary. INT #8 is used, because one CP/M-68 implementation uses INT #2 for CP/M calls. I don't know if INT #8 is a good choice or not. I'm open to alternate suggestions.
On 12/23/2011 06:44 PM, John Monahan wrote:
I have not begun to work on CP/M-68. This BIOS should have the basic console I/O calls, and disk I/O calls needed for any OS. CP/M is probably the easiest to get running; but I am open to other OS suggestions.Thanks John. Unfortunately I am a little confused where to go from there. I think I can write code to do console I/O and talk to the dual IDE board (with CF cards) but how do I splice this BIOS into the generic CPM68K. Where do you have that.
Working with the 8259A on a Z80, I totally gave up trying to vector interrupts in mode 2. That is why I moved to the NS32202 interrupt controller. On the MF/PIC board, with the "configuration register" this controller will cause the board to give interrupt responses compatible with the MC68000 family, Z80 (IM 2), and Z80 (IM 0). All 3 of these modes of operation have been tested.BTW could I run the system using an Intel 8259A is "read status mode" from a single interrupt.
The NS32202 PIC with the MF/PIC board circuitry does this all in hardware. It can be programmed to use 8 sequential Trap Vectors on the 68000, starting at an appropriate address.As you know the 8259A in it's native Intel mode puts the Int vector directly on the bus only after 3 INTA signals. However if we just trigger one the 68K Int pins we can just read the 8259A status and get appropriate S100 Int (1-7). Slower but at least generalized.
The NS32202 looks rather daunting to initialize. However, NS provides an initialization flowchart in the data sheet. That is why the initialization code, posted with the MF/PIC board docs, is specified in C. There are comments for the changes needed for the Z80.
The S-100 system may use a different PIC. The differences should be handled in the BIOS; the OS need never know what PIC is actually in use, if any. Auto-vectoring operation ought to be a good choice with the 68000 also.
John John Monahan Ph.D mon...@vitasoft.org -----Original Message----- From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com] On Behalf Of John Coffman Sent: Friday, December 23, 2011 4:44 PM To: n8vem...@googlegroups.com Subject: Re: [N8VEM-S100:566] S-100 68K CPU board status John, Start at http://n8vem-sbc.pbworks.com/ Under the tab "Pages & Files", folders to traverse are: 1 Board Information 2 ECB Processor Boards 3 ECB Baby 68000 direct link board description: http://n8vem-sbc.pbworks.com/w/file/48863865/baby%20M68K%20descr.txt 4 BIOS ROM images direct link BIOS docs: http://n8vem-sbc.pbworks.com/w/file/48864762/BIOS_doc.zip Bios 8 is the latest posted. --John On 12/23/2011 02:10 PM, John Monahan wrote:John could you direct me to the most relevant URL for the ECB baby M86K Thanks John John Monahan Ph.D mon...@vitasoft.org -----Original Message----- From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com] On Behalf Of John Coffman Sent: Friday, December 23, 2011 12:04 PM To: n8vem...@googlegroups.com Subject: Re: [N8VEM-S100:564] S-100 68K CPU board status John, The ECB baby M68k approach has been to write a BIOS that can load from CF card. The next round of the BIOS will have Floppy support (1.2Mb, 720Kb, 1.44Mb). I haven't tackled CP/M-68 yet; but I don't see it as very difficult to support above the BIOS level. Ultimately I'd like to see real CP/M diskettes supported: 128 bytes/sector FM mode. --John On 12/23/2011 09:38 AM, John Monahan wrote:Hi Guy's, While waiting for a few components to arrive for the S-100 VGA prototype board (very slow here this time of the year, very frustrating), I have been browsing the web looking for the easiest way in software to get CPM68K running with our 68K board, ZFDC board etc. Has anybody done this in the classical way, i.e. write a BIOS is assembler link it in with DR's code, place it on a 8" disk and get going from there. Most of what I see is in C code and/or requires aCPM68K OS already running to get going.John John Monahan Ph.D mon...@vitasoft.org -----Original Message----- From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com] On Behalf Of Andrew Lynch Sent: Friday, December 23, 2011 7:00 AM To: n8vem...@googlegroups.com Subject: [N8VEM-S100:562] S-100 68K CPU board status Hi Mike! We made some changes to the third prototype to add the TMI circuitry and remove some of the redundant debugging hardware. You'll notice the board is using the DIP-64 version of the CPU so it is back to closer to your MMU design. The PCB is taking forever to clean up the trace routing although recently it is showing signs of improvement. Slowly though... Please keep up with the MMU design because there is going to be an S-100 68K CPU board eventually! Thanks and have a nice day! Andrew Lynch [snip] PS. Sorry I've been slacking on the 68K work, guys, I've been just up to my neck, it's getting closer to the front burner however. Mike Sharkey http://8bit.zapto.org