Functional Description
2.4.3
µP Access to B and IC Channels
In IOM-2 terminal mode (TE mode, SPCR:SPM=0) the microprocessor can access the B and
IC (intercommunication) channels at the IOM-2 interface by reading the B1CR/B2CR or by
reading and writing the C1R/C2R registers. Furthermore it is possible to loop back the
B-channels from/to the S/T interface or to loop back the IC channels from/to the IOM-2
interface without µP intervention.
These access and switching functions are selected with the Channel Connect bits (CxC1,
CxC0) in the SPCR register (table 4, figure 34).
External B-channel sources (voice/data modules) connected to the IOM-2 interface can be
disconnected with the IOM off function (ADF1:IOF) in order to not disturb the B-channel access
(see figure 34).
If the B-channel access is used for transferring 64 kbit/s voice/data information directly from
the µP port to the ISDN S/T interface, the access can be synchronized to the IOM interface by
means of a synchronous transfer interrupt programmed in the STCR register.
Table 4
µP Access to B/IC Channels (IOM®-2)
C×C1 C×C0 C×R
C×R
B×CR Output Applications
to
Read Write Read IOM-2
0
0
1
0
1
0
IC×
IC×
–
–
B×
B×
B×
–
B× monitoring, IC× monitoring
IC×
B×
IC×
B×
B× monitoring, IC× looping from/to IOM-2
B× access from/to S
transmission of a constant value in
B× channel to S
0
;
0
1
1
B×
B×
–
B×
B× looping from S
transmission of a variable pattern in
B× channel to S
0
;
0
Note: x=1 for channel 1 or 2 for channel 2
The general sequence of operations to access the B/IC channels is:
(set configuration register SPCR)
Program Synchronous Interrupt (ST0)
>
SIN –
Read Register (B×CR, C×R)
(Write register)
Acknowledge SIN (SC0)
Semiconductor Group
68
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