psf21911 ETC-unknow, psf21911 Datasheet - Page 83

• Manufacturer Part Number: psf21911
• Description: Isdn Echocancellation Circuit Terminal Applications Iec-q
• Manufacturer: ETC-unknow

PSB 21911
PSF 21911
Access to IOM-2 Channels
of the FIFOs are parallely shifted to DRU and DRI respectively. DRU and DRI have to be
read before the next interrupt ISTA:D can occur, otherwise 8 bits will be lost. DWU and
DWI have to be loaded with data for 4 IOM-frames. Data in DWU and DWI is assumed
to be valid at the time ISTA:D occurs. The register contents are shifted parallely into two
2-bit FIFOs of length four, from where the data is put to IOM-2 and U respectively during
the following 4 IOM-frames. During this time, new data can be placed on DWU and DWI.
DWU and DWI are not cleared after the data was passed to the FIFOs. That is, a byte
may be put into DWU or DWI once and continously passed to IOM or U, respectively.
Figure 27 illustrates this procedure:
Figure 27 Procedure for the D-Channel Processing
Note: Default of DWU, DWI, DRU and DRI after reset is "FF
".
H
2.6.3
C/I Channel Access
Setting SWST:CI to "1" enables the microprocessor to access C/I-commands and
indications between IOM-2 and the U-transceiver.
A change in two consecutive frames (double last look) in the C/I-channel on IOM-2 is
indicated by an interrupt ISTA:CICI. The received C/I-command can be read from
register CIRI. A change in the C/I-channel coming from the U-transceiver is indicated by
an interrupt ISTA:CICU. The new C/I-indication can be read from register CIRU .
Note: The term C/I-indication always refers to a C/I-code coming from the U-transceiver,
whereas the term C/I-command refers to a C/I-code going into the U-transceiver.
A C/I-code going to the U-transceiver has to be written into the CIWU-register. A C/I-
code to IOM-2 has to be written into the CIWI-register. The contents of both registers
(CIWU and CIWI) will be transferred at the next available IOM-2 frame. The registers are
not cleared after the transfer. Therefore, it is possible to continously send C/I codes to
IOM-2 or the U-transceiver by only writing the code into the register once.
Semiconductor Group
83
11.97