;  LoadExtraBanks.asm
;   (LoadExtraBanksX.asm does not provide the fake BootMain exports)

; last edited by :
; -- murage 13-Feb-84 10:19:58 - fixed so that it lies where Burdock version lies.
; -- murage 18-Oct-83 15:29:21 - commented out calls to MP code and also
;				 made bank byte a variable.
; -- Sturgis:   16-Sep-83 16:16:39

	get	"SysDefs.asm"
	get	"BootDefs.asm"
	get	"BootLinkDefs.asm"
	
; LoadExtraBanksHandle will place a jmp to NewNextPhaseCodeProlog at 2000H
; actually, for a first try this code will be loaded at 2000H, since this code will not be running when domino is loaded, so domino can load right on top of it.

	EXP	NewNextPhaseCodeProlog
	
; this module is expected to be loaded with BootSubs
	
	IMP	CheckCPStopped, GetNextWord, IncrMP, PhaseToMP 
	IMP	StartCP, StartNextRead, TransferCSImage, TransferTPCImage


; Boot subs needs the following, but will not actually use it

	EXP	StartIOPBoot, StartNextPhase

; this definition is for Burdock
StartIOPAddressHigh	equ	StartIOPAddress+1
	
; this definition logically belongs in BootDefs, among CPKernelconstants
CPSetBank	equ	02H	; command to Kernel to Set the bank register
CPKernelTest	equ	03H	; command to Kernel to see if FakeKernel is present

;this is the bank to be loaded next.

BankNo:		db	0		;jmm  9-Feb-84 17:03:46

NewNextPhaseCodeProlog:

; compute address of StartBootBlock in BootMain
	lhld	DoBootPhaseExt+1
	lxi	b, 3
	dad	b
prol1:	shld	StartBB+1

; change StartIOPAddress
prol2:	lxi	h, NewNextPhaseCode
	shld	StartIOPAddress
	
	
	
NewNextPhaseCode:
;	jmp	StartBB;  %% mod purcell 14 may 84
	
;prol4:	call	CheckCPStopped;  put it into Kernel if not already there
;	call	TestForMyKernel;	see if all is well
;prol5:	call	StepBank;
;	call	TestForMyKernel;	see if all is well
	call	TransferCSImage;	low CP memory, including idle loop
;	call	TestForMyKernel;	see if all is well
	call	StartCP;	safe now that idle loop in the new bank
	
	lxi	h,1
	call	StartNextRead
	lxi	h,Header
	call	GetNextWord;	skip over check sum word of last .db

; now we know that both my Kernal and the (cp) IOP (task 5) is working, lets try shutting down and starting up again

;	call	CheckCPStopped
;        call	TestForMyKernel
;	call	StartCP;
	
	call	InitTPCsOnly;	reset the TPCs, don't init the image
	
; the address is loaded during prolog

StartBB:
	jmp	0	; jmp BootMain.StartBootBlock, don't init the image
	
	
		
; init only the TPCs, do not change the low CP mem image
; this code copied from BootSubs, extracted from InitCSTPCImage
;  Initialize the TPC array with all slots empty, i.e. high bit of word = 1.

InitTPCsOnly:
	mvi	c,8		;  Counter for 8 words
	mvi	e,0		;  Initialize TPC slot to 8000H (empty)
	mvi	d,80H
	lxi	h,TPCBuffer	;  Start of Buffer
InitTPCImageLoop:
	mov	m,e		;  Store low byte
	inx	h
	mov	m,d		;  Store high byte
	inx	h
	dcr	c		;  More TPC's?
	jnz	InitTPCImageLoop	;  nz =>  More to do
	ret


; request the Kernel to advance the bank register

StepBank:
	mvi	a, CPSetBank	
	call	WriteCPbyte
	lda	BankNo
	call	WriteCPbyte
	call	ReadCPbyte
	sta	LatestBank
	ret
	

; see if my FakeKernel is really running
TestForMyKernel:
	mvi	a, CPKernelTest
	call	WriteCPbyte
	call	ReadCPbyte
	mvi	b, 7
	cmp	b
	rz		; Kernel Present

KernelNotPresent:
 	jmp	KernelNotPresent

; following exists in BootSubs, but not exported

; Subroutine:  WriteCPbyte.
;  Write CP byte.
;  Byte in A register written into port.
WriteCPbyte:
	out	CPOut		;  Output data
WaitCPOutAck:
	in	CPStatus	;  Read the port interrupt bits
	ani	CPOutIntMask	;  CPOut requesting an interrupt, i.e data read? 
	jz	WaitCPOutAck	;  Zero means no interrupt
	ret

; following exists in BootSubs, but not exported

; Subroutine:  ReadCPbyte.
;  Read CP byte.
;  Byte returned in A register.
ReadCPbyte:
	in	CPStatus	;  Read the port interrupt bits
	ani	CPInIntMask	;  CPIn requesting an interrupt? 
	jz	ReadCPbyte	;  Zero means no interrupt
	in	CPIn		;  get data
	ret



;DATA section:

; this is for debugging to see if correct bank was loaded.

LatestBank:
	db	07FH
	

; following code is to satisfy the imports of boot subs

StartIOPBoot	dw	0;	this is only used during boot initialization, so not used
StartNextPhase	dw	0;	also applies to this word


	
	END	LoadExtraBanks