13

DA9191A.000

July 31, 1997

FUNCTIONS

After a reset the TX block is in power down. The

power down mode is controlled by bit TXSIP (TX

collision occurs or for any other TX block reset

causes. When the device is ready to receive data,

begins. The data is transferred from the serial

interface to the TX buffer and the TXWRD bit is set

high again, which causes XINT to become active.

When the block comes out of power down mode the

XINT is active because the device is ready to receive

data (TXWRD goes high). The lower nibble of the

fifth byte is ignored. The 36 bits of data are coded by

the BCH coder with following polynomial:

G(x) = x

The BCH coder adds 12 parity bits to the data and

the data is transferred to the DCC coding block. The

DCC coder adds a digital color code on the reverse

control channel (RECC) according following table.

DCC(1:0)

Coded DCC

00

0000000

01

0011111

10

1100011

11

1111100

The framing block adds bit sync (101010...10) and word sync (11100010010) sequences to the frames and

performs needed repeats depending on the mode.

Reverse control channel data format. The numbers under the frames show the number of bits in each section.

Bit sync

Word sync

Coded DCC

First word

repeated 5 times

Second word

repeated 5 times

30

11

7

240

240

Reverse voice channel data format.

Bit Sync

Word

Sync

1.Repeat

of word 1

Bit Sync

Word

Sync

2.Repeat

of word 1

Bit Sync

Word

Sync

101

11

48

37

11

48

37

11

Bit Sync

Word

Sync

5.Repeat

of word 1

Bit Sync

Word

Sync

1.Repeat

of word 2

Bit Sync

Word

Sync

37

11

48

37

11

48

37

11

Bit Sync

Word

Sync

5.Repeat

of word 2

37

11

48

The Manchester encoder block encodes the data into

a Manchester coded format with bit clock. The bit

clock is 8kHz in the ETACS mode and 10kHz in the

AMPS mode. The mode can be controlled by bit

bit does not go active between 56 and 104 bits of the

transmitted message a transmission collision occurs.

In this case the data which is in the TX block and the

data that the user is writing to the device will not be

high in this case and cause an interrupt. The TXCOL

will remain active until the TX block is reset with the

transmitter off when a TX collision occurs. If the

audio block is muted with switch S19 on the voice

channel while data transmission is occurring.