FX919A Datasheet, PDF (19/44 Pages) CML Microcircuits – 4-Level FSK Modem Data Pump

4-Level FSK Modem Data Pump
FX919A
TIB: Transmit Intermediate Block
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.
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'.
TLB: Transmit Last Block
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.
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'.
T4S: Transmit 4 Symbols
This command is similar to T24S but takes only one byte from the Data Block Buffer, transmitting it as four 4-
level symbols.
RESET: Stop any current action
This 'task' takes effect immediately, and terminates any current action (task, AQSC or AQLEV) 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
when VDD is applied, to set the modem into a known state.
Note that due to delays in the transmit filter, it will take several symbol times for any change to appear at the
TXOP pin.
© 1996 Consumer Microcircuits Limited
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