CMX148 datasheet(49/75 Pages) CMLMICRO

49 / 75 page

PMR Audio and Data Processor

CMX148

D/148/6

8.1.24.

Modem Control - $C7 write

SynC SynD SynT

En_

RAW

Last

Data

Inter-

leave

MSK/FFSK Message

Format

User

Bit

Scramble

Seed

This register configures the way the CMX148 handles MSK data in Tx and Rx modes.

b15 SynC detect (MSK/FFSK) 0 = off

1 = enabled

b14 SynD detect (MSK/FFSK) 0 = off

1 = enabled

b13 SynT detect (MSK/FFSK)

0 = off

1 = enabled

note: SynC, SynD and SynT patterns are defined in Program Block P0.0-3

b12 reserved

b11 reserved

b10 En_RAW:

0 = data packetising on

1 = raw data mode

This selects the raw or formatted mode for type 0 MSK/FFSK or DSC data.

MSK/FFSK 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

b10 = 0: device will look for a complete Frame Head before raising an interrupt (if enabled)

and then decode the following data in accordance with the received message format. The

Frame Head Control Field bytes, user data and any CRC will be presented in the appropriate

Rx Data registers ($C5 and $C9).

MSK/FFSK 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.

b10 = 0: device will transmit the programmed bit and frame sync patterns followed by a Frame

Head containing the information supplied in bits 7–0 of this register and the 2 bytes in Tx Data

1 register ($CA). Subsequently the host must supply data when requested to complete the

transmission of the Frame Head and Data Block.

Last Tx data:

This is only valid when transmitting data with Formats 0, 2 or 3 in MSK/FFSK modes and

indicates to the CMX148 that it can cease modulation. The host must set this bit to 1

immediately after the interrupt for ‘load more data’ occurs ($C6 bit 6). In receive, or when

transmitting other message formats, this bit must be cleared to 0.

Interleave:

0 = off

1 = on

This bit selects if Frame Headers in MSK/FFSK modes will be interleaved or not.

b7-5 Data Format:

Format Message Format

Raw Data (En_RAW = 1)

Frame Head only, no payload

Frame Head + Unsized payload of raw 16 bit words

Frame Head + Unsized payload with FEC

Frame Head + Sized payload with FEC + CRC

Frame Head + Sized payload with FEC + CRC + interleaving

All other patterns

reserved

reserved, clear to 0.

b2 User bit.

May be freely used by the host in MSK/FFSK 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.

CMX148 Datasheet(PDF) 49 Page - CML Microcircuits

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