Functional Description
2.3.7
MONITOR Channel Handling
The MONITOR channel in IOM-1 mode is used for the exchange of control information
between the ISDN Communication Controller ICC (PEB 2070) and layer-1 devices like the
ISDN Burst Controller IBC (PEB 2095) or the ISDN Echo Cancellation circuit IEC (PEB 2090).
Since the ISAC-S combines the functions of the ICC and the S Bus interface Circuit SBC (PEB
2080) and since the SBC does not use the MONITOR channel for data transfers, there is
usually no necessity for performing MONITOR channel operations with the ISAC-S in IOM-1
mode.
The implemented MONITOR handler of the ICC is however fully operational and can therefore
be used in conjunction with external layer-1 transceivers in case only the ICC part of the
ISAC-S is used (ADF1:TEM).
Prerequisite for data transfers over the monitor channel is an appropriate code in the MODE
register e.g. MODE:DIM2-0 = 010 or 011.
Only one byte of information at a time can be transferred between the ISAC-S and another
device.
The procedure is as follows:
MONITOR Transmit Channel (MOX) register is loaded with the value to be sent in the outgoing
MONITOR channel. (Bytes of the form FX are not allowed for this purpose because of the
H
TIC bus collision resolution procedure).
The receiving device interprets the incoming monitor value as a control/information byte, FX
H
excluded. If no response is expected, the procedure is complete. If the receiving device does
react by transmitting information to the ISAC-S, it should set the E bit to "0" and send the
response in the monitor channel of the following frame.
The ISAC-S
– latches the value in the MONITOR channel of the frame immediately following a frame with
"E=0" into MOR register.
– generates a MONITOR Status interrupt MOS (EXIR register) to indicate that the MOR
register has been loaded. See figure 23.
MON
IDP1
IDP0
X
X
Y
E
0
MON
E
0
MON
=
F
H
MOR Load, MOS Int.
MOR Load, MOS Int.
ITD00868
Figure 23
MONITOR Channel Protocol (IOM®-1)
Semiconductor Group
54
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