>Compared to some of the other things you've been expressing
>interest in recently, the stack should be pretty easy.

Yeah I kinda figured. I've pretty much got the push/pop thing
down now. This is kinda what I'm doing so far :

INIT_CARD:
	MOV	A,	#149
	Push	Acc	
        MOV	A,	#0
	Push	Acc
	Push	Acc
	Push	Acc
	MOV	A,	#64
	PUSH	ACC
	LCALL	CONTROLCARD
	RET

CONTROLCARD:
	SETB	Dout
	CLR	CS
	MOV	R2,	#6   ; 6 bytes to transfer to card
	LCALL	SENDSPI
	SETB	CS
	RET

SENDSPI:
	MOV	R3,	#8
	POP	ACC
	CLOCKBYTE:
	RLC	A
	MOV	DIN,	C
	SETB	SPICLK
	CLR	SPICLK
	DJNZ	R3,	CLOCKBYTE
	DJNZ	R2,	SENDSPI
	SETB	DIN

So far this -should- load the 6 bytes into the stack, leaving
them to be pulled off the stack in transmission order (ie: 40h 00h 00h 00h 00h 95h) and rotate them left through C so they are MSB first, as I believe the datasheets say it should be.
The last line in SENDSPI: is SETB DIN, which, again, -should- go high after everything is clocked out. Now I'm just kinda confused as to how many clocks I have to send before a reponse is to be received. I love diving into datasheets. Not. You'll notice the SENDSPI has no RET, since this is now where I should start receiving information... Not done yet :)

My biggest confusion in ASM is lines like "MOV A,@R0". I know
that means A will contain whatever value is at memory location
defined in R0, rather than the value of R0 itself, but I just get stuck on this sometimes.

One important question, if the A is "pushed" onto the stack... does that set A back to 00h, or does A retain the value it had in it from before the push?