FX919B Datasheet, PDF (19/47 Pages) CML Microcircuits – Excellent Radio Fading Performance

4-Level FSK Modem Data Pump
FX919B
'Frame Sync'
Symbols
-1 +1 -1 +1
-1 +3 -3 +3
-3 -1 +1 -3
+3 +3 -1 +1
-3 -3 +1 +3
-1 -3 +1 +3
Values written to Data Block Buffer
Binary
Hex
Byte 0:
00100010
22
Byte 1:
00110111
37
Byte 2:
01001001
49
Byte 3:
11110010
F2
Byte 4:
01011011
5B
Byte 5:
00011011
1B
THB: Transmit Header Block
This task takes 10 bytes of data (Address and Control) from the Data Block Buffer, calculates and appends the
2-byte CRC1 checksum, translates the result to 4-level symbols (with FEC), interleaves the symbols and
transmits the result as a formatted 'Header' 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'.
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.
© 1997 Consumer Microcircuits Limited
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D/919B/1