ABOOTSIM.ASM

ABOOTSIM.ASM VERSION 1.0 10/27/76 JRB

3 IMSAI CP/M SIMULATOR FOR AUTOMATIC BOOTSTRAP

THIS PROGRAM IS ONLY NEEDED TO START CP/M COLD

IF YOU DO NOT YET HAVE THE NEW AUTOMATIC BOOTSTRAP

FIRMWARE INSTALLED IN YOUR DISC INTERFACE.

THE FUNCTION OF THIS PROGRAM IS TO READ DRIVE 0,

3 TRACK a, SECTOR I INTO RAM LOCATIONS

a To 7FH THEN JMP To 0.

THIS IS THE FANCY VERSION,

SUITABLE FOR USE IN ROM AND WITH ERROR RECOVERY.

BBASE EQU ROOOH ;ORIGIN AND STARTING ADDRESS EXIT EQU o ;wHERE THIS PROGRAM EXITS To DISK EQU OFDH ;COMMAND PORT FOR FLOPPY DISC BCMD EQU 80H ;BEGINNING OF DISC COMMAND STRING

AND COMMAND BYTE THEREOF

BSTAT EQU BCMD+1 ;STATUS BYTE... I BTRK EQU BCMD+2 ;TRACK (2 BYTES) IBSECT EQU GCMD+4 ;SECTOR BBUFAD EQU BCMD+5 ;BUFFER ADDRESS ORG BBASE

3

START HERE

3

3 SET FLOPPY DISC INTERFACE STRING POINTER

MVI A,IOH ;COMMAND TO SET STRING POINTER 0 our DISK ;SEND IT ‘ LXI H,BCMD ;POINT H AT COMMAND STRING

Mov A,L 5L0 ORDER STRING ADDRESS

OUT DISK

Mov A,H ;HI ORDER STRING ADDRESS

OUT DISK

ABOOTSIM.ASM CONTINUED

SET UP STRING IN RAM

5

MVI M,21H INX H

COMMAND TO READ SECTOR, UNIT 0

,POINT AT STATUS BYTE 5(3TATUS BYTE WILL BE ZEROED LATER)

INX H ,POINT AT HI ORDER TRACK

XRA A ;CET 0 IN A

Mov M,A 3ZERO HIGH ORDER TRACK

INX H

MOv M,A ;ZERO LO ORDER TRACK

INX H

MVI M,1 ;SECTOR 1

INX H

Mov M,A ;2ERO LO ORDER BUFFER ADDRESS INX H

Mov M,A ;ZERO HIGH ORDER BUF ADDRESS

INITIALIZATION COMPLETE. NOW READ SECTOR.

REPEAT: LXI

WAIT:

H,BSTAT XRA A . MOV M,A ;STATus MUST BE 0 BEFORE COMMAND

N. B. A=o IS DISK COMMAND TO EXECUTE STRING 0

OUT DISK 3TELL DISK TO GO!

ADD M ;LOOK FOR NON-0 STATUS

JZ WAIT ;KEEP LOOKING TILL IT COMES

CPI I ;ONLY CORRECT RETURN VALUE IS 1 J2 EXIT ;ON SUCCESS, TRANSFER CONTROL

CP/M BOOTSTRAP ROUTINE READ IN FROM DISK

DISK ERROR HAS OCCURED. -

3 DISPLAY ERROR CODE IN LIGHTS AND KEEP TRYING.

V. 50 5.

THUS IF DISK IS NOT READY, CP/M WILL BOOT AS SOON AS IT COMES READY.

CMA 5LIGHTS DISPLAL COMPLEMENT

OUT OFFH 5OUTPUT A TO "PROG OUTPUT" LIGHTS MVI A,21H ;RESTORE DRIVE 1 - IT HELPS!

OUT DISK ;SEND RESTORE COMMAND TO DISK

JMP REPEAT 3TRY AGAIN (AND AGAIN, AND ...)

END BBASE