CMX625D5 CML Microcircuits, CMX625D5 Datasheet - Page 13

• Manufacturer Part Number: CMX625D5
• Description: ISDN TA POTS Interface
• Manufacturer: CML Microcircuits

ISDN TA POTS Interface
1.5.5
In order to be able to identify different devices on the IOM-2 bus, an identification command is sent. This
allows the software to identify different manufacturer's devices on the bus. The identification sequence is
usually done once, when the device is connected for the first time.
A device requesting the identity of a connected CMX625 will transmit the following 2 byte command:
The CMX625 responds by transmitting:
SA(2-0) = Slot Address, DS = Device Select (see sections 1.5.2 and 1.5.3). See section 1.5.14 for the
Device Identification Register.
1.5.6
The PCM Codec-Filter performs voice digitisation and reconstruction and incorporates encoder bandpass
and decoder lowpass filters with pre and post-filtering with selectable A-law and µ-law companding. In
each case the coder and decoder process a companded 8-bit PCM word following CCITT
recommendation G.711 for A-law and µ-law conversion. The encoder bandpass filter and decoder
lowpass filter provide passband flatness and stopband rejection according to CCITT recommendation
G.712. The lowpass filter contains the required (Sin X)/X compensation. The overall filter characteristics
of the channel are shown in Figure 12.
The PCM Codec-Filter block is enabled or disabled by bit 7 of the CODEC CONTROL Register. The
companding law is selected by bit 6. When this bit is a ‘0’, A-law companding is selected (used in
Europe) and when this bit is a ‘1’, µ-law is selected (used in the USA and Japan).
The PCM Codec Channel routeing is shown in the table below for normal operation and bus reversal. In
‘normal’ operation, bit 4 of the IOM Control Register is set to ‘0’, the data is transmitted on the Data
Upstream (DU) pin and received on the Data Downstream (DD) pin. Bits 6 and 7 of the IOM Control
Register select whether the data is transmitted or received on the B1, B2, IC1 or IC2 channels of the
IOM-2 bus. The B1 and B2 channels are available in TE and non-TE mode but the IC1 and IC2 channels
are only available in TE mode.
DD 1
DD 2
DU 1
DU 2
2000 Consumer Microcircuits Limited
st
nd
st
nd
Monitor Channel Identification Command
PCM Codec-Filter
byte
byte
byte
byte
Bit7
Bit7
1
0
1
1
SA2
SA2
Bit6
Bit6
0
0
Figure 8 Abort Request from the Receiver
SA1
SA1
Bit5
Bit5
0
0
Data
MX
MR
SA0
SA0
Bit4
Bit4
0
1
Byte 1
Bit3
Bit3
DS
DS
0
1
13
Bit2
Bit2
0
0
0
0
Byte 2
Bit1
Bit1
Abort Request
0
0
0
0
EOM
Bit 0
Bit 0
0
0
0
1
Monitor Channel Address Byte
Device Identification Byte
CMX625
D/625/1