ISDN TA POTS Interface
CMX625
The CMX625 is programmed via the ‘MON1’ (Monitor Channel 1) channel in TE mode and the ‘Monitor’
channel in non-TE mode. The programming sequence consists of 3 consecutive Monitor bytes: the IOM-2
address, the CMX625 command and data byte. Before executing a command, the CMX625 compares the
received IOM-2 address byte with its own address. The MSB of the IOM-2 address is always a ‘1’ (see
section 1.5.2). A logical ‘1’ in the MSB of the CMX625 command represents a write operation and a
logical ‘0’ represents a read operation.
Structure for Register read/write operations:
IOM
R/W
Register Register Register Register
Command 0=Read
0
X
X
Address Address Address Address
Register 1=Write
A3
A2
A1
A0
Example 1: Program the CMX625 to generate interrupt requests for DTMF RX Status Change on bit 5 of
C/I channel, i.e. C/I1 Channel Output Control Code (2-0)=110. Set IOM-2 address to SA2-SA0=010 and
device select, DS=1.
MX MR
(DD) (DU)
11
01
00
10
01
10
01
10
11
01
00
10
01
10
01
10
11
11
DD
(hex)
FF
A8
A8
88
88
06
06
FF
FF
A8
A8
89
89
20
20
FF
FF
FF
MX MR
(DU) (DD)
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
DU
(hex)
FF
FF
FF
FF
FF
FF
FF
FF
FF
FF
FF
FF
FF
FF
FF
FF
FF
FF
Comment
Monitor Channel Idle State
Transmit IOM-2 Address
Acknowledge Address
Transmit Command (Write IOM-2 Control, $8)
Acknowledge Command/ Transmit IOM-2 Control Data
Acknowledge Data
End of Transmission
Transmit IOM-2 Address
Acknowledge Address
Transmit Command (Write Mask Register, $9)
Acknowledge Command/ Transmit IOM-2 Control Data
Acknowledge Data
End of Transmission
Idle
If the command is a register read then only the address and command bytes are sent. The CMX625 will
respond with an IOM-2 Register address byte followed by the read data. The IOM-2 Register address byte
consists of the Register address that is being read in the least significant 4 bits and the IOM-2 address
(less the device select bit) in the most significant 4 bits.
2001 Consumer Microcircuits Limited
21
D/625/2