CMX969D5 MX-COM, Inc., CMX969D5 Datasheet - Page 13

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

MOTIENT
4.5.2.3
This bit should always be set to ‘0’ for standard RD-LAP and MDC systems. Setting it to ‘1’ in RD-LAP mode
selects an alternative CRC generation/checking algorithm.
4.5.2.4
This bit should always be set to ‘0’ for standard RD-LAP and MDC systems. Setting it to ‘1’ in RD-LAP mode
selects slightly different transmit and receive lowpass filter characteristics more suitable for some non-
standard systems.
4.5.2.5
If this bit is ‘0’ the CMX969 operates in RD-LAP mode, setting this bit to ‘1’ selects MDC mode. Changing
between RD-LAP and MDC modes will cancel any current task.
4.5.2.6
In RD-LAP mode, this bit affects the number of errors tolerated by the Frame Sync detector. The allowable
errors are approximately 3 bits when FSTOL = 0, 7 bits when FSTOL = 1. In MDC mode, this bit has no effect
and the Frame Sync detector will accept up to 5 incorrect bits in a received Frame Sync pattern.
4.5.2.7
Setting this bit to 1 disables the receive level and symbol timing error correction circuits.
4.5.3
The contents of this 8-bit write only register control the basic operating modes of the modem:
4.5.3.1
When this bit is set to '1', the IRQ chip output pin is pulled low (to V
Register is a '1'.
4.5.3.2
This bit controls the polarity of the transmitted and received symbol voltages.
4.5.3.3
Setting this bit to '1' puts the modem into Transmit mode, clearing it to '0' puts the modem into Receive mode.
Note that changing between receive and transmit modes will cancel any current task.
¤ ¤ ¤ ¤ 2001 MX-COM, Inc.
4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA
SM
Mode Register
/ARDIS
Control Register B4: ALTCRC - Alternative CRC
Control Register B3: ALTFILT - Alternative Filtering
Control Register B2: MDC - MDC Mode
Control Register B1: FSTOL - Frame Sync Detect Tolerance
Control Register B0: HOLD - Freeze Rx Level and Timing Corrections
Mode Register B7:
Mode Register B6: INVSYM - Invert Symbols
Mode Register B5:
SM
RD-LAP
B6
0
1
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TM
MDC4800 Modem
IRQEN
Mode Register
'+3 or +1'
'+3 or +1'
Symbol
'-3 or -1'
'-3 or -1'
IRQ
TX/
7
RX
INVSYM
EN
6
- Tx/Rx Mode
- IRQ Output Enable
TX/RX
5
Signal at TXOUT
Above V
Above V
Below V
Below V
ZP
4
13
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PSAVE
BIAS
BIAS
BIAS
BIAS
3
SSIEN
2
SS
) whenever the IRQ bit of the Status
Signal at RXFB
1
SSYM
Above V
Above V
Below V
Below V
0
BIAS
BIAS
BIAS
BIAS
CMX969 Advance Information
Doc. # 20480211.002