Marine VHF Audio and Signalling Processor
CMX885
8.1.23 Modem Configuration – $C7 write
15
14
13
12
En
NWR
11
10
9
Last
Tx
8
0
7
0
6
0
5
0
4
0
3
0
2
1
0
0
En
En
User
Bit
SynC SynD SynT Data DSC RAW Data
0
This register configures the way the CMX885 handles DSC data in Tx and Rx modes.
b15 SynC detect
b14 SynD detect
b13 SynT detect
0 = off
0 = off
0 = off
1 = enabled
1 = enabled
1 = enabled
note: SynC, SynD and SynT patterns are defined in Program Blocks P0.0-3
b12 En_NWR_data 0 = disabled 1 = enabled
The En_NWR_data bit is required to disable the NWR SAME data decoder at the end of a data
frame. The decoder will detect and respond to the arrival of a sync signal (if $C1:b12 is set to
1), and report any following data, however the host will need to decode the data from the
CMX885, recognise the end of data and then disable the SAME decoder through this bit.
Setting this bit to 1 will disable the sync search and output data immediately.
b11 En_DSC data mode
0 = disabled
1 = enabled
Setting this bit selects DSC modem operation. The Modem Enable bit $C1:b2 will start/stop the
modem.
b10 En_RAW:
0 = data packetising on 1 = raw data mode
This bit selects the raw or formatted (data packetising) mode for DSC data.
DSC Receive mode:
b10 = 1: device will look for the programmed Frame Sync. pattern, raise an interrupt (if enabled)
and decode the following data 16 bits at a time, making them available in Rx Data 1 register
($C5).
DSC Transmit mode:
b10 = 1: device will transmit data 16 bits at a time from Tx Data 1 register ($CA). Bit and frame
sync pattern generation and all formatting of the data have to be performed by the host in this
case.
b9 Last Tx data:
This is only valid when transmitting data in DSC formatted mode and indicates to the CMX885
that it can cease modulation. The host must set this bit to 1 immediately after the interrupt for
‘load more data’ occurs $C6:b6. In receive, or when transmitting other message formats, this
bit must be cleared to 0.
b8-3 reserved, clear to 0
b2 User bit.
May be freely used by the host in DSC modes. This bit has no effect on the message format or
encoding and will be reported in the Rx Data 1 register for the receiving host to use as
appropriate. This bit could be used to indicate a special message, e.g. one containing handset
or channel set-up information.
b1-0 reserved, clear to 0
8.1.24 Programming Register – $C8 write
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Program Block Address
Program Block Data
See section 8.2 for a definition of program block operation.
8.1.25 Tx Data 1 – $CA write
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Bit:
$CA
flag
DSC Character 0
flag
DSC Character 1
© 2010 CML Microsystems Plc
46
D/885/3
CMLMICRO [ CML MICROCIRCUITS ]
