MX429A データシートの表示（PDF） - MX-COM Inc

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MX429A

1200/2400bps MSK Modem for Trunked Radio Systems

MX-COM Inc  

1200/2400bps MSK Modem for Trunked Radio Systems

6

MX429A

4 General Description

4.1 Modems in Mobile Data Signaling

4.1.1 Digital Code Format

The MPT 1327 Signaling Standard for Trunked LMR Systems protocol is used by the MX429 for

communication between a Trunking System Controller (TSC) and users' radio units. These data stream

formats are summarized in Figure 3.

Preamble

For bit sync.

101010...10..- bit reversals

Minimum 16 bits, ending in

logic'0'

SYNC or SYNT

SYNC Word

1100010011010111

SYNT Word

0011101100101000

Address Code

Word

64 Bits

Optional Data

Code Words

Address Code Word Structure

Bit No.

1

2 to 8

No. of Bits

1

7

Bit Name

Logic '1'

User Identity

9 to 48

40

Address

&

Data

(Bit number 1 is transmitted first)

49 to 64

16

Check Bits

(Checksum)

Figure 3: Tx and Rx Data Stream

4.1.2 Operation

The MX429A can be used for Full-Duplex operation with the host microprocessor only having to operate on

the data while the modem (MX429A) handles all other signaling routines and requirements.

In the Tx mode the MX429A will :

1. Internally generate and transmit a preamble – bit reversals, for system bit synchronization.

2. Accept from the host, and transmit, a 16-bit 'SYNC' or 'SYNT' word.

3. Accept from the host, and transmit, 6 bytes of data (Address Code Word):

A. Upon a software command, internally calculate and transmit a 2-byte checksum based on the

previous 6 data bytes.

B. Upon a software command, disable internal checksum generation and allow continuous data

transmission.

4. Transmit 1 'hang bit' and go idle when all loaded data traffic has been sent (followed by a "Tx Idle"

interrupt).

In the Rx mode the MX429A will:

1. Detect and achieve bit synchronization within 16 bits.

2. Search for and detect the 16-bit 'SYNC'/'SYNT' word.

3. Output all received data after 'SYNC/SYNT,' in byte form.

4. Upon a software command (Rx Message Format), use the received checksum to calculate the

presence (if any) of errors, and advise the host with an interrupt and a 16-bit Syndrome word.

Note: In Rx, a software command is used to determine whether a 'SYNC'/'SYNT' word is required after

every 8 (6 data + 2 checksum ) received bytes, or "data" is received continually.

Normally the 'SYNC' word is used on the Control data channel and the 'SYNT' word is used on the

Traffic data channel.

© 1998 MX-COM Inc.

www.mxcom.com Tel: 800 638-5577 336 744-5050 Fax: 336 744-5054

Doc. # 20480128.007

4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA

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