CMX969 Consumer Microcircuits Limited, CMX969 Datasheet - Page 17

• Manufacturer Part Number: CMX969
• Description: RD-LAP/MDC4800/Motient/ARDIS4-Level FSK Packet Data Modem
• Manufacturer: Consumer Microcircuits Limited

RD-LAP/MDC4800 Motient/ARDIS
This lets the µC write a task and the associated data to the modem while the modem is still transmitting the
data from the previous task.
T24S: Transmit 24 Symbols (RD-LAP only)
This task, which is intended to facilitate the transmission of Symbol and Frame Sync patterns as well as
special test sequences, takes 6 bytes of data from the Data Block Buffer and transmits them as 24 4-level
symbols without any CRC, FEC, interleaving or adding any 'S' symbols.
Byte 0 of the Data Block Buffer is sent first, byte 5 last.
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', indicating to the µC that it may write the data and command byte for the next task to
the modem.
The following tables show what data has to be written to the Data Block Buffer to transmit the CMX969
Symbol and Frame Sync sequences:
2001 Consumer Microcircuits Limited
Once all of the data has been transferred from the Data Block Buffer the modem will set the BFREE
and IRQ bits of the Status Register to '1', (causing the chip IRQN output to go low if the IRQNEN bit of
the Mode Register has been set to '1') to tell the µC that it may write new data and the next task to the
modem.
+3
+3
+3
+3
+3
-3
'Symbol Sync'
+3
+3
+3
+3
+3
Symbols
-3
+3
-3
-3
-3
-3
-3
+3
-3
-3
-3
-3
-3
Figure 7 Transmit Task Overlapping
Byte 5 :
Byte 0:
Byte 1:
Byte 2:
Byte 3:
Byte 4:
Values written to Data Block Buffer
17
11110101
11110101
11110101
11110101
11110101
01011111
Binary
Hex
F5
F5
F5
F5
F5
5F
CMX969
D/969/5