BBC micro compatible - Keypad interface. By Lee Davison.
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This is the CUBE keypad interface. This is a single board computer in it's own right. It uses the Rockwell R6501AQ 'One-Chip Microprocessor' which, while very similar to the 6502, boasts four 8 bit I/O ports, one of which can be latched, two 16 bit counter/timers, 192 bytes of RAM, 32 of which can be battery backed, a UART and four edge triggered interrupt inputs.

It also has two extra instructions for setting and resetting individual memory or register bits, and two extra branch instructions for testing the state of individual bits in registers or memory.

Another difference from the 6502 is the stack which is in page zero. This allows the R6501 to run with no external RAM at all.

The A version of the chip, which this is, runs at 2MHz (4MHz XTAL) and is in the unusual Quad in line package. The board contains the following...

R6501AQ CPU

16k EPROM

2 x relays

2 x RS422/485 drivers

AMPAL16L8

Misc 74 and 4000 series logic

7 x 2N7000 MOSFETs

I've done a dump of the 27128 16k EPROM that contains the interface code. You can download it as either a binary dump or Motorola S record.

Download the interface EPROM as a zipped Motorola S record file.

Download the interface EPROM as a zipped binary dump.

There is also an AMPAL16L8. You can download the jdec fuse file for it here.

Download IC7 as a jdec fuse file.

I've completed a commented assembly listing for the EPROM contents above. The 16k byte EPROM is almost empty, only 534 bytes being used.

Read it as html here, or download it as a zipped file here.

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