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A breakdown of the serial data protocol used in the UNIDEN Scanning Mobile Receiver model MR8100
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Data Protocol

Serial port parameters:

Baud Rate Parity Data Bits Stop Bits
1200 NONE 8 1

NOTE: Data can not be sent to the radio if it happens to be locked on to the priority channel. Make sure the Priority indicator is off (press ‘PRI’).

Every character sent to the radio is echoed back to the PC. It is therefore important to always flush the input buffer and “confirm” the received characters match those sent.

There are two types of commands that can be sent to the radio:
1 Program a Channel / Bank Label / Priority; (send 21 bytes):     <CC> <type> <EE> <data> <text>
2 Request data from the radio; (send 3 bytes):     <DD> <type> <EE>
… then the radio responds with 18 bytes: <data> <text>
Where the <CC>, <DD>, and <EE> are single byte values 20410, 22110, and 23810 respectively.

In the table above, the <type> (1 byte): is one of 3 choices: Priority or Bank Label or Channel

Where <0x>, <bc> and <Bb> are bytes containing the following nibbles (4 bits):

  • <text>; (14 bytes)…

    16 ASCII characters are “compressed” to 14 data bytes. This is possible because only 7 out of 8 bits per byte are used (value 0 to 127). Because the high bit <7> is always 0 (unused) the bytes are left-shifted. The vacated least significant bit <0> is then used to squeeze in an extra character longitudenally. In summary:

    1. Characters 0 – 6 shift left by 1
    2. Vacated bit <0> of these characters is transposed character 7: bits <6> to <0> respectively
    3. Characters 8 – 14 shift left by 1
    4. Vacated bit <0> of these characters is transposed character 15: bits <6> to <0> respectively

    Allowable characters in text are ASCII in the range 3210 to 12710, with the following exceptions:
    Character Decimal Displayed as
    \ 92 (yen)
    ~ 126 (right arrow)
    (del) 127 (left arrow)

    There are no descenders for the letters: g, j, p, q, y. They do not display well.

    After sending data to the radio, unlock it (continue scanning) by sending a 0 byte.



    This page originally posted on 03-Jan-2008