ISDN TA POTS Interface
CMX625
EOM
MX
Data
MR
Byte 1
Byte 2
Abort Request
Figure 8 Abort Request from the Receiver
1.5.5 Monitor Channel Identification Command
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:
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit 0
DD 1st byte
DD 2nd byte
1
0
SA2 SA1 SA0
DS
0
0
0
0
0
0
0
0
0
0
The CMX625 responds by transmitting:
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit 0
DU 1st byte
DU 2nd byte
1
1
SA2 SA1 SA0
DS
1
0
0
0
0
0
1
Monitor Channel Address Byte
Device Identification Byte
0
0
1
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 PCM Codec-Filter
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 ITU-T 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 ITU-T 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.
2001 Consumer Microcircuits Limited
13
D/625/2
CMLMICRO [ CML MICROCIRCUITS ]
