Sorry...I'm using two AT89S8252 microcontrollers from Atmel.

http://www.atmel.com/dyn/resou...oc0401.pdf

(pages 9-10, 18-19 are pertinent to SPI)

As far as the code goes, I'll be happy to include as much as anyone thinks would be helpful; however, I think this is almost certainly some sort of hardware problem with the 8051 since the problem occurs *during* the byte-transmission. Is there a way that I can post a screen-shot of my logic analyzer on this message board?

Here's my initialization for the slave:
mov spcr,#01001001b

Here's my initialization for the master:
mov spcr,#01011001b

Here's how I output from the slave:
mov dptr,#start_wireless_audio ; point to message
call spi_msg_out

---
spi_msg_out:
clr a ; reset counter to 0
movc a,@a+dptr ; read byte from code
jz spi_msg_out_done ; check for eom
call spi_io ; send byte out
inc dptr ; point to next byte
jmp spi_msg_out ; loop back
spi_msg_out_done:
ret
---

---
spi_io:
macro_debug_out spi_io_out_msg
call debug_hex_out

mov spdr,a ; send the byte
spi_io_loop:
mov a,spsr ; read the spi status register
anl a,#SPIF_MASK ; check the spif bit
jz spi_io_loop ; wait for tx/rx to complete
mov a,spdr ; read in the received byte
call debug_hex_out
macro_debug_out spi_io_in_msg

spi_io_done:
ret
---