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