Functional Description
2.3.4
SSI (Serial Port A)
The SSI (Serial Synchronous Interface) is available only in timing mode 0 (SPCR:SPM=0).
The serial port SSI serves as a full duplex connection to B-channel sources/destinations in
terminal equipment with a data rate of 128 kbit/s.
Both channels B1 and B2 can be switched independently of one another to the IOM-1 interface
and thus to the S/T interface (SPCR:CxC1, CxC0).
In case of the PEB 2086, the B1- and B2-channels are handled as one 128-kbit/s channel. The
data transfer between SSI an IOM is shown in figure 22d.
The SSI consists of one data line in each direction (SDAX and SDAR), an 8-kHz strobe output
(FSC1 and/or FSC2) and the 128-kHz clock output (SCA).
B-Channel Source/Destination
SSI
ISDN Sunscriber Access
SDAR
128 kbit/s
128 kbit/s
ISAC R -S
Timing Mode 0
TE Mode
SDAX
SCA
Voice/Data
Module
128 kHz
8 kHz
FSC1/2
S
SDAR, X
B2
B1
)
*
FSC1/2
) Default Polarity
(ADF1 Register)
*
ITS00857
Figure 19
Connection of the B-Channel Sources/Destinations to the ISAC®-S via SSI
This serial interface allows the connection of Voice/Data modules, such as serial synchronous
transceiver devices (USART’s, ICC PEB 2070, HSCX SAB 82525, ITAC®, PSB 2110...) and
various CODEC filters directly to the ISAC-S, as illustrated in figure 19.
By programming the ADF1 register it is possible to independently set the strobe signal FSC1/
2 polarities so that either B1 or B2 is selected by the V/D module.
The µC system has access to B-channel data via the ISAC-S registers BxCR and CxR.
The µC access must be synchronized to the serial transmission by means of the Synchronous
Transfer Interrupt STCR (see chapter 4).
Semiconductor Group
46
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