ISDN TA POTS Interface

CMX625

 2001 Consumer Microcircuits Limited

10

D/625/2

(v) The ‘Intercommunication Channel’ consists of two 64kbps data channels, labelled IC1 and IC2, and

provide additional communications paths between devices other than the layer 1 device (data to and

from the layer 1 device is transferred over the B channels).

(vi) The ‘TIC’ (Terminal IC) bus is used for connecting more than one device to the D and C/I0 channels

in Channel 0. The TIC bus is not used by the CMX625.

1.5.3

Non-Terminal Mode (non-TE)

The non-TE mode (Line Card Mode) frame structure consists of up to 8 channels of 4 bytes each repeated

at 8kHz, i.e. 256 bits in 125

µs or a data rate of 2048kbps for 8 channel frames. The Data Clock (DCL)

operates at twice the data rate, i.e. 4.096MHz. Figure 4 shows the non-TE mode frame structure.

M

X

M

R

L

S

B

M

S

B

M

X

M

R

L

S

B

M

S

B

CH0

CH1

CH2

CH3

CH4

CH5

CH6

CH7

CH0

DD

CH0

CH1

CH2

CH3

CH4

CH5

CH6

CH7

CH0

DU

FSC

DCL

125µs

B1

B2

MONITOR

C/I

B1

B2

MONITOR

C/I

D

for analogue lines

for ISDN lines

FSC

= 8kHz

DCL

= 4.096MHz

DD, DU = 2048kbps

Figure 4 Non-Terminal Mode Frame Structure

In non-TE mode the IOM-2 bus time multiplexes data, control and status information for up to eight IOM-2

devices or up to 16 Codec-Filters over a single full duplex interface. The frames are subdivided into 8

channels, with one channel being dedicated to each IOM-2 device or pair of Codecs.

Each device on the IOM-2 bus is assigned a slot address and only transmits to and receives from that time

slot. Pins SA0, SA1 and SA2 on the CMX625 are used to program the Slot Address. Outside the

allocated slot the transmit drivers will be set to high impedance to allow other devices to transmit in their

own time slot. To allow two CMX625 devices to share the same slot a Device Select pin (DS) is made

available. This pin forms part of the Monitor Channel Address Byte along with the Slot Address pins and

allows either of the two devices sharing a slot to be individually addressed. See section 1.5.2, part (ii)

MON Channel Address Byte. This mechanism allows both the B1 and B2 data from the same time slot to

be utilised by different devices.