PAL-2

15-18 januari 2025 At the time of writing this page the PAL-2 has just been available for sale, I am waiting for my kit!
So this information is based upon the available documentation: User manual, Schematic, BOM.
The PAL-2 is for sale by Liu Ganning at Tindie

On this page:

What is a PAL-2?
The PAL-2 is a kit for an SBC in the now large family of KIM-1 clones. Ranging from the Micro-KIM to the PCB exact replica by Eduardo Casino, all share the KIM-1 ROMs, LED display and TTY interface and the 6532 RIOT instead of the 6530 RRIOT.

What makes the PAL-2 unique:

  • It is a real and complete KIM-1 clone.
  • Available as a DIY kit with high quality components.
  • The layout is close to the KIM-1.
  • The good looking keypad is very close to the KIM-1
  • Application and Expansion connector with all relevant KIM-1 signals.
  • Lots of RAM in many configurable options.
  • Both RRIOTS 6532 on board.
  • TTY interface on TTL level, USB to TTL adapter included in the kit, quality serial!
  • Power can come from the USB to TTL adapter or from external 5V supply (same as for the KIM-1)

The PAL-2 differs from a KIM-1

  • No Audio cassette interface for file I/O circuit, but see below for a solution
  • Application and Expansion connector as 22×2 pinheader instead of PCB edge connectors
  • The signals on the Application connector are not all identical: no audio, TTY instead of 20 mA loop, decoding lines added
  • Not the same size PCB

The PAL-2 differs from the PAL-1:
The many quality improvements and enhancements make the base PAL-2 kit more expensive then a base PAL-1 kit.
If you expand the PAL-1 to the level of a PAL-2 you need to spend money on a motherboard, a RAM 32K, a second RRIOT kit, an RS232 cable and gender changer and a 9V power supply.

  • Improved keypad, with labels and look of the KIM-1
  • No need for a Motherboard
    • No external RAM module required
    • No external RRIOT required
  • E000-FFFF can be used freely from ROM expansion
  • The vectors (Reset, NMI, IRQ) can be placed in external ROM.
  • Looks a lot more like a KIM-1
  • Complete Application and Expansion connector
  • TTY on TTL level instead of (not standard) RS232



Schematic

PAL-2 User Manual


RAM decoding
The PAL-2 has a very flexible RAM memory layout, as shown in the next parts of the schematics:



Internal ROM and external ROM
The PAL-2 has a 2K ROM with the KIM-1 monitor. Since there is no audio in and outcircuitry, the ROM from 1800-1BFF could be used for other programs, like the KIM Clone by Corsham Technology (Which also did not have the audio circuitry). The 28C16 is easy to program.

One of the first expansions that is to be expected is an external 8K ROM. The decoding for this ROM, e.g. an 28C64 is already present on the connectors and in the decoding circuit.
The decoding signals are 8K7_SELECT (CE on 28C64) and 8K7_ROM (OE on 28C64). Just the 28C64 IC has to be connected to address and data lines.


Application and Expansion connectors


KIM-1 Application connector


Differences on the Application connector with the KIM-1:

  • AUDIO IN -> 8k7_SELECT
  • AUDIO OUT LO -> 8K7-ROM
  • TTY in and out now at TTL level for USB to TTL converter
  • TTY PTR and KYBD, +1wV, AUDIO OUT LO not connected

This means, even if the edge to pin connector issue is solved, the standard KIM-1 I/O boards will not work for TTY and audio.

The expansion connector is identical to the KIM-1.


KIM-1 Expansion connector


Power supply
Power has to be applied in the standard KIM-1 manner to the application connector Pin 1 = GND, pin A = 5V.
Note that reversing these pins will mean the dead of the PAL-2!


Expansion

As a first suggestion for a PAL-2 extension I see a board connected to Application and Extension connectors with: