CMX969D5 MX-COM, Inc., CMX969D5 Datasheet - Page 26

• Manufacturer Part Number: CMX969D5
• Description: MOTIENT/ARDIS RD-LAP MDC4800 Modem
• Manufacturer: MX-COM, Inc.

MOTIENT
4.6.5.7
In receive RD-LAP mode these two bits reflect the value of the latest received 'S' symbol. In transmit mode,
these two bits will be '0'.
4.6.5.8
In receive MDC mode this bit reflects the type of Frame Synchronization pattern received:
4.6.5.9
In receive MDC mode this bit reflects the value of the latest received channel status bit. In transmit mode, this
bit will be '0'.
4.6.6
In receive mode, the CMX969 continually measures the 'quality' of the received signal, by comparing the
actual received waveform against an internally generated 'ideal' 2 or 4-level FSK baseband signal.
The result is placed into bits 3-7 of the Data Quality Register for the µC to read at any time, bits 0-2 being
always set to '0'. Figure 14 shows how the value (0-255) read from the Data Quality Register varies with
received raw (uncorrected) bit error rate:
The Data Quality readings are only valid when the modem has successfully acquired signal level and timing
lock for at least 64 symbol times. A low reading will be obtained if the received signal waveform is distorted in
any significant way.
¤ ¤ ¤ ¤ 2001 MX-COM, Inc.
4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA
SM
‘0’ indicates Frame Sync SYNC1 ($07092A446F, MSB first)
‘1’ indicates Frame Sync SYNC2 (logical inverse of SYNC1)
Data Quality Register
/ARDIS
Status Register B1, B0: RD-LAP Mode: SVAL - Received 'S' Symbol Value
Status Register B1: MDC Mode: Received Frame Sync Type
Status Register B0: MDC Mode: SBIT - Received Channel Status Bit
SM
1.E-01
1.E-02
1.E-03
1.E-04
1.E-05
1.E-06
RD-LAP
Figure 14: Typical Data Quality Reading vs. BER (uncorrected)
0
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TM
MDC4800 Modem
50
Average DQ Reading
100
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200
CMX969 Advance Information
Doc. # 20480211.002
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