Oh, while I think of it Phil, do you have the gear to check what the glue logic presents on the low eight data lines during sample reads? The DSP wants 16-bit signed samples, and the ROM contains 8-bit signed samples that need to end up in the most significant byte. I want to know what ends up in the least significant byte (I'm emulating it as byte smearing).

The lines in question are RB00 to RB07, on pins 35, 36, 37, 38, 39, 40, 42 and 43 (information manual p7-7 or 162 in PDF numbering). I want to know if they're always tied high/low, or if they're somehow affected by what's on lines RB08 to RB15, on pins 44, 45, 46, 47, 48, 49, 50 and 51. The DSP samples RB00 to RB15 on falling edges of the CKO output (pin 33, see p7-10/165). There are no read/write strobes as it's designed to be used with dumb ROM.