CMX969D5 MX-COM, Inc., CMX969D5 Datasheet - Page 18

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

MOTIENT
4.6.1.5
In RD-LAP mode this task takes 12 bytes of data from the Data Block Buffer, updates the 4-byte CRC2
checksum for inclusion in the 'Last' block, translates the 12 data bytes to 4-level symbols (with FEC),
interleaves the symbols and transmits the result as a formatted 'Intermediate' Block, inserting 'S' symbols at
22-symbol intervals.
In MDC mode this task takes 6 bytes of data from the Data Block Buffer, updates the 2-byte CRC checksum
for inclusion in the 'Last' block, adds FEC bits, interleaves the result, inserts channel status bits and transmits
the result as a formatted ‘Intermediate’ Block.
Once the modem has read the data bytes from the Data Block Buffer, the BFREE and IRQ bits of the Status
Register will be set to '1'.
4.6.1.6
In RD-LAP mode this task takes 8 bytes of data from the Data Block Buffer, updates and appends the 4-byte
CRC2 checksum, translates the resulting 12 bytes to 4-level symbols (with FEC), interleaves the symbols and
transmits the result as a formatted 'Last' Block , inserting 'S' symbols at 22-symbol intervals.
In MDC mode this task takes 4 bytes of data from the Data Block Buffer, updates and appends the 2-byte
checksum, adds FEC bits, interleaves the result, inserts channel status bits and transmits the result as a
formatted ‘Last’ Block.
Once the modem has read the data bytes from the Data Block Buffer, the BFREE and IRQ bits of the Status
Register will be set to '1'.
4.6.1.7
This task is similar to T24S but takes only one byte from the Data Block Buffer, transmitting it as four 4-level
symbols most significant bit first.
4.6.1.8
This task is similar to T40B but takes only one byte from the Data Block Buffer, transmitting it as 8 bits.
4.6.1.9
This task takes 3 ID bytes from the Data Block Buffer, calculates and appends the 6-bit CRC0 checksum,
translates the result to 4-level symbols (with FEC) and transmits the resulting 22 symbols preceded and
followed by 'S' symbols.
Once the modem has read the data bytes from the Data Block Buffer, the BFREE and IRQ bits of the Status
Register will be set to '1'.
4.6.1.10 RESET: Stop any current action
This 'task' takes effect immediately, and terminates any current task the modem may be performing and sets
the BFREE bit of the Status Register to '1', without setting the IRQ bit. It should be used (after a delay to allow
the Xtal oscillator to start up) when V
set the modem into a known state.
Note that due to delays in the transmit low pass filter, it will take several symbol times for any change to
appear at the TXOUT pin.
¤ ¤ ¤ ¤ 2001 MX-COM, Inc.
4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA
SM
/ARDIS
TIB: Transmit Intermediate Block (RD-LAP and MDC)
TLB: Transmit Last Block (RD-LAP and MDC)
T4S: Transmit 4 Symbols (RD-LAP only)
T8B: Transmit 8 Bits (MDC only)
TSID: Transmit Station ID (RD-LAP only)
SM
RD-LAP
www.mxcom.com Tel: [phone] 744 5050 Fax: [phone]
TM
MDC4800 Modem
DD
is applied or the ZP bit of the Mode Register changed from ‘1’ to ‘0’ to
18
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CMX969 Advance Information
Doc. # 20480211.002