I have a couple of these , I think they are 8051 core , you could do a bb mcu / serial programmer , but you need > 24 I/O pins , TX RX and a clock and Vpp I started way back using an 8255 ! perhaps now a PIC16F877 could do it , the encryption bytes may be an issue if it has them ?
think this is right....
Quick-Pulse Programming
The setup for microcontroller quick-pulse programming is shown in Figure 26. Note that the device is running with a 4 to 6 MHz
oscillator. The reason the oscillator needs to be running is that the device is executing internal address and program data transfers.
The address of the EPROM location to be programmed is applied to ports 1 and 2, as shown in Figure 26. The code byte to be
programmed into that location is applied to port 0. RST, PSEN and pins of ports 2 and 3 specified in Table 8 are held at the ‘Program
Code Data’ levels indicated in Table 8. The ALE/PROG is pulsed low 5 times as shown in Figure 27.
To program the encryption table, repeat the 5 pulse programming sequence for addresses 0 through 1FH, using the ‘Pgm Encryption
Table’ levels. Do not forget that after the encryption table is programmed, verification cycles will produce only encrypted data.
To program the security bits, repeat the 5 pulse programming sequence using the ‘Pgm Security Bit’ levels. After one security bit is
programmed, further programming of the code memory and encryption table is disabled. However, the other security bits can still
be programmed.