PRO2006.2

Mod#6 : 6400 channel memory capacity (ADVANCED TECHNICIANS ONLY!)
Parts : Hitachi HM62256LFP-12 (256Kx8 SRAM) or equivalent (flat pack required)
        4 Position DIPswitch
        10KOhm resistor SIP  (or 4 10K 1/8w resistors)

        This modification is complicated, so don't try it if you're not fully
        sure of youre ability.


        1) Remove front panel from scanner, disconnect wiring harnesses.
           You will lose all current programs (Sorry!)

        2) Remove metal shield from panel CAREFULLY!
           Remove screws holding CPU board in front panel.
           Carefully separate CPU board from keyboard.

        3) Locate IC505 next to CPU and remove it from the board.
           Notice this is a 24pin IC, and that there are 4 extra pads
           to the top of pin 1. All pin numbers given hereafter will
           refer to the new 28 pin IC, with pin 4 being the old IC's
           pin 1. Follow me? The pads for the new IC are already present.

        4) To adapt to the new RAM, a few traces must be sliced.

           A) Slice the trace connecting pin 28 to pin 26
           B) Slice trace connecting pin 27 to pin 23 (bottom of board)
           C) Slice trace connecting pin 2 to ground (bottom of board)

        5) Install the new RAM, and connect a jumper from CPU IC501
           pin 67 (+5V) to pin 28 of the new RAM.

        6) To address the extended memory, external switches must be added
           and connected to the unused address lines of the new RAM.
           Just how you implement this is up to you. Regardless of how you
           do it, you will need to connect a wire bundle from the new RAM
           pins 1,2,23,26 to the outside world. I mounted a jack on the rear
           panel into which a 4 position dipswitch can be mounted.

        7) Add pullup resistors from new address lines to +5V, available at
           pin 3 of the +5V regulator IC8.

        8) Reassemble unit, installing all shields and ground straps.

        9) Testing & checkout

           A) With all switches 'OFF' enter '1000.000' into memory channel 1.
           B) Toggle switch 1 to on and return to channel 1. Enter '1001.000'
           C) Repeat for all switch combinations. Lockout channel 1 in each
              of the 16 memory blocks. You now have a coded channel to key
              you in on which block you're scanning.
           D) Enjoy 6400 channels of pure scanning power!


        You now have:

            16 Blocks of 400 memory channels per block
           160 Search ranges (10 per block)
           160 Temporary scratchpad channels (10 per block)

        Notice that custom settings (delay/mode) are unique to EACH
        channel, but priority and speed are common to all blocks.
        You might dedicate a common channel in each block to be the
        priority channel