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A breakdown of the serial data protocol used in the UNIDEN Scanning Mobile Receiver model MR8100 Author Unknown

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…

• <0x> – Priority; <data>; (4 bytes): <bc>, <?>, <bank 1–8>, <bank 9,10>
  This sets or shows the priority channel assignment and the current active banks. Also sets or shows 16 character “hidden” text for auxilliary usage.
  • <bc> see below
  • <?>: 0 (unknown)
  • <bank 1–8>; (1 byte): bits are as follows:
    • <0> – bank 5
    • <1> – bank 6
    • <2> – bank 7
    • <3> – bank 8
    • <4> – bank 1
    • <5> – bank 2
    • <6> – bank 3
    • <7> – bank 4
  • <bank 9,10>; (1 byte): bits are as follows:
    • <0> – ? (default to 0)
    • <1> – ? (default to 0)
    • <2> – ? (default to 0)
    • <3> – ? (default to 0)
    • <4> – bank 9
    • <5> – bank 10
    • <6> – ? (default to 0)
    • <7> – ? (default to 1)
• <Bb> – Bank Label; <data>; (4 bytes): 0, 0, 0, 0
  This sets or shows the text associated with the bank. This is displayed briefly when a bank is switched to “active” during scanning by pressing a number key.
• <bc> – Channel; <data>; (4 bytes): <flags>, <band>, <freq1>, <freq2>
  This sets or shows the channel frequency and additional attributes. Text may be numeric representation of frequency or any arbitrary channel label.
  
  
• <flags>; (1 byte):
  

  Bit(s)	Description
  <3:0>	0 (unknown)
  <4>	channel is not locked out: 0, channel is locked out: 1
  <5>	not USED: 0, USED: 1
  <6>	not SECURE: 0, SECURE: 1
  <7>	0 (unknown)

  • Not USED means that channel can not be unlocked from the keyboard unless a new frequency is programmed.
  • SECURE means that channel can not be altered from the keyboard.

  <band>; (1 byte):

  Bit(s)	Description
  <0>	IF shift: set to 1 for band 0, otherwise 0 for other bands
  <1>	set to 1 for 118–135.995, otherwise 0 (this may be the AM / FM switch)
  <3:2>	0: 29 – 135.995 MHz (5 kHz spacing, 0.4 µV sensitivity) 1: 136 – 174 MHz (5 kHz spacing, 0.5 µV sensitivity) 2: 406 – 512 MHz (12.5 kHz spacing, 0.5 µV sensitivity) 3: 806 – 956 MHz (12.5 kHz spacing, 0.6 µV sensitivity)
  <4>	12.5 kHz decrement (range 806 – 956 MHz, see below)
  <7:5>	0 (unknown)

  <freq1>, <freq2>; (total 2 bytes):
  This is a 16 bit unsigned integer – most significant byte followed by least significant byte.

  This integer is calculated from the frequency. There are three different calculations depending on the band in which the frequency lies.

  Frequency in MHz	band byte		Formula	Result Integer	Theoretical Frequency Range	Channel Step
  	<3:2>	<0>
  29 – 135.995	0	1	F x 200 + 2170	7970 – 29369	-10.85 – 316.8250	5 kHz
  136 – 174	1	0	F x 200 - 2170	25030 – 32630	10.85 – 338.5250	5 kHz
  406 – 512	2	0	F x 80 - 868	31612 – 40092	10.85 – 830.0375	12.5 kHz
  806 – 956 *	3	0		31806 – 37806	10.85 – 1649.2250	12.5 kHz

  ^* For the range 806 – 956 MHz perform the additional calculations with the result integer:

  1. If integer is odd – add 1 to it, set bit <4> of band byte.
  2. Divide the integer by 2 (always)

  Note: according to specifications, 10.85 MHz is the receivers intermediate frequency.

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

• x – arbitrary value
• B – actual hex (11 decimal)
• b – bank number 1 to 10 (1 – A₁₆)
• c – channel number 1 to 10 (1 – A₁₆)