FX929A Datasheet, PDF (19/44 Pages) CML Microcircuits – 4-Level FSK Modem Data Pump

4-Level FSK Modem Data Pump
FX929A
'Symbol Sync'
Symbols
+3 +3 -3 -3
+3 +3 -3 -3
+3 +3 -3 -3
+3 +3 -3 -3
+3 +3 -3 -3
-3 -3 +3 +3
Values written to Data Block Buffer
Binary
Hex
Byte 0:
11110101
F5
Byte 1:
11110101
F5
Byte 2:
11110101
F5
Byte 3:
11110101
F5
Byte 4:
11110101
F5
Byte 5 :
01011111
5F
'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 , inserting 'S' symbols at 22-symbol intervals.
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 , inserting 'S' symbols at 22-symbol intervals.
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 , inserting 'S' symbols at 22-symbol intervals.
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 task is similar to T24S but takes only one byte from the Data Block Buffer, transmitting it as four 4-level
symbols.
© 1996 Consumer Microcircuits Limited
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D/929A/4