PEF2091 Siemens Semiconductor Group, PEF2091 Datasheet - Page 99

• Manufacturer Part Number: PEF2091
• Description: ICs for Communications(ISDN Echocancellation Circuit)
• Manufacturer: Siemens Semiconductor Group

4.1.2
Setting SWST:D to "1" enables the microprocessor to access D-channel data between
the IOM
Four registers (see Table 15) handle the transfer of data from IOM
µP to IOM
"D-Channel Access Registers", page 221 for more details about these registers.
.
Table 15
Register
DWU
DRU
DWI
DRI
Two 2-bit FIFOs of length 4 collect the incoming D-channel packets from IOM
Every fourth IOM
the contents of the FIFOs are shifted in parallel 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
DWI is assumed to be valid at the time ISTA:D occurs (see also "Interrupt Structure",
page 209). The register contents are shifted in parallel into two 2-bit FIFOs of length four,
from where the data is put to IOM
following 4 IOM
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 continuously passed to IOM
core, respectively. Figure 40 illustrates this procedure:
Figure 40
Note 29: Default of DWU, DWI, DRU and DRI after reset is "FF
Semiconductor Group
®
-2 and the transceiver core.
®
D-Channel Access
-2, from the µP to transceiver core and from transceiver core to the µP. See
Arriving D-Channel Bits
D-Channel Data Registers
Procedure for the D-Channel Processing
Function
write D-channel data to transceiver core
read D-channel data from transceiver core
write D-channel data to IOM
read D-channel data from IOM
®
-2-frames. During this time, new data can be placed on DWU and DWI.
®
-2-frame when they are filled, an interrupt ISTA:D is generated and
2 Bits
®
-2 and transceiver core respectively during the
DWU or DWI
DRU or DRI
®
99
-2
®
-2
ITD08120
®
-2-frames. Data in DWU and
Leaving D-Channel Bits
Operational Description
H
®
".
-2 to the µP, from the
®
-2 or transceiver
Data Sheet 01.99
PEB 2091
PEF 2091
®
-2 and U.