AVR-Chat

Hmm.. Having much fun trying to implement this..

The basics of the Xmodem transfer protocol are working, and I get 128 
byte packets from the host.

But putting them into program memory isn't working out right.

I have a register that counts packets from the host, of course it 
rolls at 255, so I grab another register that counts rollovers.  1024 
packets of 128 bytes fills a M128.  Here's how I translate the packet 
count to the write address:

;
;***********************************************************
;
; Create the page pointer in three DIFFERENT registers.
; from the Xmodem packet count, and ITEMP, which is used
; as the high byte, since we have no INTS at this point.
;
Loader_MakePage:
	lds	TEMP,XmodemBlk		;
	call	Pong			;

	clr	ZL			;
	out	RAMPZ,ZL		;
	;   RAMPZ       ZH       ZL
	;00000000 xxxxxxxx 00000000

	lds	ZH,XmodemBlk		;The packet number
	;00000000 pppppppp 00000000

	dec	ZH						;
	;packet 1 goes to block zero
	;00000000 bbbbbbbb 00000000

	lsr	ZH					
	;shifts a 0 into MSB of ZH
	ror	ZL					
	;shifts carry into MSB of ZL
	;   RAMPZ       ZH       ZL
	;00000000 0bbbbbbb b0000000
	;       |          ||    ||
	;       |          ||    |\----- Which byte within word
	;       |          |\----\------ Words within page
	;	\----------\------------ Pages

	mov	TEMP,ITEMP	;UGLY fix for how they bastardized the
	andi	TEMP,$03	;000000xx
	breq	MakePage_NOZ	;If neither bit is set, then done.

	sbrc	TEMP,0		;If lsb is set, then set MSB of ZH
	ori	ZH,$80		;dosen't touch TEMP
	;00000000 Bbbbbbbb b000000

	sbrs	TEMP,1		;if b1 is set, then set B0 of RAMPZ
	rjmp	MakePage_Noz	;
	ldi	TEMP,$01	;
	out	RAMPZ,TEMP	;

	;00000001 Bbbbbbbb b0000000
	;       |          ||    ||
	;       |          ||    |\----- Which byte within word
	;       |          |\----\------ Words within page
	;       \----------\------------ Pages

MakePage_Noz:
	in	TEMP,RAMPZ	;So I can see the adrs on the LA
	call	PONG
	mov	TEMP,ZH
	call	Pong
	mov	TEMP,ZL
	call	Pong
	ret
;
;***********************************************************
;

What's happening, is that it seems to be erasing EVERY page, but 
writing every OTHER page, although I can't tell if it's wrapping, or 
exactly what is going on..  The "pong" statements are my byte in PWM 
output on a single pin, and that shows me what I expect as the 
packets come in.