Design Ideas: January 20, 1994
The circuit in Fig 1 emulates 8-kbyte PROMs, such as the 2764. The programs in Listings 1 and 2 allow you to download a PROM program to the emulator via a PC's serial port.
To operate the emulator, you first set the SPST switch to the closed, or download, position. The PC then downloads the PROM's data via the emulator's 8751 microcontroller. Moving the switch back to the open position puts the circuit in emulation mode.
The compressed ZIPfile, DI1346Z.ZIP, attached to the message /DI_SIG #1346, contains Listings 1 and 2 as well as executable files and an OrCAD 2.0 version of the schematic in Fig 1.