DA9191A.000
July 31, 1997
FUNCTIONS
◆ Data Transmission
After a reset the TX block is in power down. The
power down mode is controlled by bit TXSIP (TX
section in power down) in register 07HEX. The TXRST
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:
bit located in register 12
is used every time a TX
HEX
collision occurs or for any other TX block reset
causes. When the device is ready to receive data,
the TXWRD bit of register 10HEX is high. If five bytes
are written into register 19HEX the data transmission
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.
G(x) = x12 + x10 + x8 + x5 + x4 + x3 + x0
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
0000000
0011111
1100011
1111100
00
01
10
11
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
Second word
repeated 5 times repeated 5 times
30
11
7
240
240
Reverse voice channel data format.
1.Repeat
2.Repeat
of word 1
Bit Sync
Word
Sync
11
Bit Sync
Word
Bit Sync
Word
Sync
11
Word
Sync
11
of word 1
48
Sync
11
101
37
Bit Sync
48
37
Bit Sync
5.Repeat
1.Repeat
Bit Sync
Word
Sync
11
Word
Sync
11
Word
Sync
11
of word 1
of word 2
37
Bit Sync
48
37
48
37
5.Repeat
of word 2
37
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
SYS0 of register 12HEX. The data polarity can be
inverted with bit INVTX of register 13HEX.If the BUSY
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
transmitted. The TXCOL bit of register 10HEX will go
high in this case and cause an interrupt. The TXCOL
will remain active until the TX block is reset with the
TXRST bit of register 12HEX. If the TXCTREN bit is
active in register 12HEX the TXCTRL output turns the
transmitter off when a TX collision occurs. If the
AUMUT bit in register 13HEX is set to high the TX
audio block is muted with switch S19 on the voice
channel while data transmission is occurring.
13
MAS [ MICRO ANALOG SYSTEMS ]
