Emulating the new (8085) CP/M

I had some problem getting CP/M to emulate with the new version of "cbios". Funny it was working before and "myEcho" is working. A day later I worked out that I had not initialised SOD during the boot process, so printing messages during the boot process did not work properly. Also, "conout" enables interrupts on return which could cause problems. Now fixed.

Disk B

For Disk B I have not installed the "boot system" so 31k of capacity is available for storage (versus 23k).

Warm Boot after Disk Select Error

I seem to have upset this so I will have to find out what I have done to upset it.

Disk A

I am pretty sure this code should still work with the updated hex files.

Finally

my CP/M 2.2 (32k)

A>DIR


A: STAT     COM
A>STAT


A: R/W, Space: 17k


A>STAT B:


Bytes Remaining On B: 9k

A>DIR B:


B: ED       COM : ASM      COM : DDT      COM : LOAD     COM
A>SAVE 3 TEMP.DAT


A>DIR


A: STAT     COM : TEMP     DAT
A>STAT


A: R/W, Space: 16k
B: R/W, Space: 9k


A>ERA TEMP.DAT


A>DIR


A: STAT     COM
A>STAT


A: R/W, Space: 17k
B: R/W, Space: 9k


A>^C
A>E:


Bdos Err On E: Select
A>B:


B>DIR


B: ED       COM : ASM      COM : DDT      COM : LOAD     COM
B>ED  DDT


DDT VERS 2.2
-L


  0100  LXI  B,0FBC
  0103  JMP  013D
  0106  MOV  B,E
  0107  MOV  C,A
  0108  MOV  D,B
  0109  MOV  E,C
  010A  MOV  D,D
  010B  MOV  C,C
  010C  MOV  B,A
  010D  MOV  C,B
  010E  MOV  D,H
-

So it appears to be working! And here it is in person:

CP/M Input Problem

I have been having problems getting programs to work. They display okay but he input is fails. Here is a typical problem:

my CP/M EMU Console - Written by Alan Cooper


my CP/M 2.2 (32k)

A>DIR
A: STAT     COM
A>STAT
A: R/W, Space: 17k


A>B:
B>DIR
B: MICRO80  COM
B>A:STAT
A: R/W, Space: 17k
B: R/W, Space: 26k


B>MICRO80

MICROCHESS                  (C) 1977.
WRITTEN BY: P. JENNINGS & T. O'BRIEN.
-------------------------------------

DO YOU WANT WHITE ? (Y,N) DO YOU WANT WHITE ? (Y,N) DO YOU WANT WHITE ? (Y,N) 

It does not recognise the character. Some programs show the character as a 'W'. This output is the actual CP/M machine but the emulator output is identical. It seems to be getting the wrong character ('W'?). I am not ready to blame ccp.asm/bdos.asm/cbios.asm just yet. I am thinking a memory clash (the stack?). For my machine I put the system very close to the top of memory, I assumed that the space was not used, perhaps I am wrong. It is where I put the ring buffer and pointers.

Gotcha

The program (micro80) overwrite RST6.5 thus I lose "getchar". This seems to be a common strategy (as it happen most of the time) to use the RST instruction to speed up the code.

That would suggest using SIM/RIM and RST6.5 for serial IO is not going to be an effective general strategy. Fine if I write my own assembler language programs.

But really I now have to use a UART and a timer. Time for the next version.

Actually after looking in the micro80.hex file I cannot find a RST instruction. Looking at the Zero Page, I can see the RST0 vector points to the program entry point and bdos vector has been overwritten. I suspect that the bdos vector has been copied.

Another problem is that code will expect a CR (0x0d) or CR/LF for CP/M and not a LF (0x0a) as for Linux. When using a terminal the line termination is configurable. But the emulator gets the LF. So really I need to insert a CR before a LF or swap the LF for a CR (in the emulator).

Success Again

After swapping LF for CR in the emulator, I loaded a very small basic like language called MINOL22:

my CP/M EMU Console - Written by Alan Cooper


my CP/M 2.2 (32k)

A>b:minol22

]10 A=0
]20 A=A+1
]30 PR "COUNT ";A
]40 IF A<10 GOTO 10
]50 END

]RUN

]LIST
10 A=0
20 A=A+1
30 PR"COUNT ";A
40 IFA<10;GOTO10
50 END

]40 IF A<10; GOTO 20
]LIST
10 A=0
20 A=A+1
30 PR"COUNT ";A
40 IFA<10;GOTO20
50 END

]RUN
COUNT  1 
COUNT  2 
COUNT  3 
COUNT  4 
COUNT  5 
COUNT  6 
COUNT  7 
COUNT  8 
COUNT  9 
COUNT  10 

]

Final Update For This CP/M Machine Version

Found a version of basic that runs on my machine (a modified version of Basic/5 for CP/M from Processor Tech):

my CP/M 2.2 (32k)

A>dir


A: STAT     COM
A>b:


B>STAT


STAT?

B>A:STAT


A: R/W, Space: 17k
B: R/W, Space: 22k


B>DIR


B: BASIC5   COM : TEST     BSC
B>BASIC5


BASIC/5 INTERACTIVE INTERPRETER    V Z1.0  10/16/77


NEW OR OLD? OLD
OLD PROGRAM NAME: TEST


READY
LIST
10 PRINT "HELLO"
20 FOR I=0 TO 10
30 PRINT I*1.6
40 NEXT I
50 END

RUN

HELLO
0 
 1.6 
 3.2 
 4.8 
 6.4 
 8 
 9.6 
 11.2 
 12.8 
 14.4 
 16 


READY
SYSTEM

B>

I think I have achieved what I have set out to do for this CP/M machine.

Next project will be a CP/M machine with a UART, a Timer, some GPIOs and bigger Flash disks (chips).

AlanX