No idea what the 74374 latch is intended for, the printer port output should be latched anyways, so it seems to be totally useless. Using SBY (instead of LRQ) means that software can't use the "1-byte FIFO" of the SP0256, which is no good (the reason for that poor design was probably that LRQ would need to be inverted by additional hardware before passing it to ACK).
For details on the speech chip, see:
* [[SP0256]]
* [[SP0256 Voice Generator]]
* [[SP0256 Allophones]]
* [[SP0256 Pin-Outs]]
* [[SP0256 on Printer Port (DIY)]]
[[Category:Music and sound]][[Category:DIY]][[Category:Printers and printer ports]]