External 8bit Printer Port from Amstrad Action Issue 38 (November 1988).
Description
This is a rather bizarre 8bit Printer Port solution. Aside from the 8th data bit, it doesn't come up with any other extras: Data is only one-directional, and only Strobe and Busy control signals are implemented.
Compared with the much older single-wire Happy Computer 8bit Printer Mod (1985), the Amstrad Action approach is terribly overcomplicated. Another downside is that the external circuit isn't backwards compatible with normal 7bit printer software.
Technical
Connects to the expansion port. Uses six TTL chips (74HC133, 74LS138, 74LS273, 74LS241, 74LS02, 74121), 4 resistors, 1 capacitor, plus some connectors.
Port Bits Expl. FBF8h N/A Strobe (W) FBF8h Bit0 Busy (R) FBF9h Bit0-7 Data (W)
Writing any value to port FBF8h issues a short Strobe signal (the length of the signal is same as /IORQ ORed with /WR).
