SPC Upload routine that doesn't crash, but whose data doesn't appear in the SMP RAM and which doesn't execute the desired offset according to the trace...

SPC Upload

namespace spc

define spcaddr #$0100
define spcexec #$0100

// DESIGN:
//      Base address for spc data is fixed
//      Specific offset is handed via X register (16bit)
//      First 2 bytes of spc data is length
//      -> ACL to 8bit, LDA spc_length -> TAY
//      -> Upload loop, via LDA {spc_data},X

upload:
	phx
	// IPL portmap outside transfer state:
	// $2141   = command (transfer / run)
	// $2142-3 = target address
	// $2140   = trigger
	rep #$20	// 16bit accumulator
	sep #$10	// 8bit x/y

	lda {spcaddr}
	sta $2142
	ldx #$01	// transfer
	stx $2141
	ldx #$cc
	stx $2140
-;	cpx $2140
	bne {-}

init:
	// IPL portmap inside transfer state:
	// $2140 = sequence number
	// $2141 = payload
	// init counters
	rep #$30	// 16bit registers
	plx
	lda $0e0000+x	// get length
	inx
	inx		// point on the beginning of data
	tay		// countdown
	sep #$20	// 8bit accumulator
	lda $0e0000+x	// get first byte of data
	sta $2141	// write to APU
	inx
	dey
	lda #$00
-;	sta $2140
	cmp $2140
	bne {-}

loop:
	lda $0e0000+x	// fill data byte
	sta $2141	// write data...
	lda $2140	// get sequence counter
	inc		// increment
	sta $2140	// write back
-;	cmp $2140	// wait for echo from IPL
	bne {-}
	inx		// increment sequence counter...
	dey
	bne loop	// if not, do it again

end:
	rep #$20
	lda {spcexec}
	sta $2142	// set exec address
	stz $2141	// command: run
	ldx $2140
	inx
	inx
	stx $2140	// send sequence end / execute
-;	cpx $2140	// wait for last echo
	bne {-}

	sep #$20
	rep #$10
	rts