The ROM
ROM types
The serial rom chip is an UV eprom NEC uPD23C1000C for foreign OZ. The UK version may be an eprom chip for v2.2, the v3.0 supports exactly the same software but have been put in a ROM which have only 28 pins. The last v4.0 is fitted on an EPROM chip. The socket layout isn't standard according to the NEC standard (see below). If you wish to fit a new eprom, be very careful, pins 2 and 24 must be exchanged according to the JEDEC standard. Particulary if you want to use actual 128K Eprom chip, like 27C1001. In theory, you can fit larger eprom (like 27C2000 or 27C4000), if you wire the addresses lines.
ROM socket
The mother has 32 pins tracked to the NEC standard.
+--------------+VCC |1 +--+ 32| VCCROE |2 31| VCCA15 |3 30| VCCA12 |4 29| A14A7 |5 28| A13A6 |6 27| A8A5 |7 Z88 26| A9A4 |8 ROM 25| A11A3 |9 PCB 24| A16A2 |10 23| A10A1 |11 22| CEA0 |12 21| D7D0 |13 20| D6D1 |14 19| D5D2 |15 18| D4VSS |16 17| D3 +--------------+
This table describes the 128K chip pinout and Blink signals.
Pin Chip Blink Pin Chip Blink1 VPP VCC 32 VCC VCC2 [OE] ROE 31 [PGM] VCC3 A15 MA15 30 VCC VCC4 A12 MA12 29 A14 MA145 A7 MA7 28 A13 MA136 A6 MA6 27 A8 MA87 A5 MA5 26 A9 MA98 A4 MA4 25 A11 MA119 A3 MA3 24 A16 MA1610 A2 MA2 23 A10 MA1011 A1 MA1 22 [CE] IPCE (Internal PROM chip enable)12 A0 MA0 21 D7 MDH13 D0 MDA 20 D6 MDG14 D1 MDB 19 D5 MDF15 D2 MDC 18 D4 MDE16 VSS GND 17 D3 MDD