Register Description
4.1.14 SAPI1 Register
SAP1
Write
Address 26
H
7
0
SAPI1
CRI
0
SAPI1 SAPI1 Value
Value of the first programmable Service Access Point Identifier (SAPI) according to
the ISDN LAPD protocol.
CRI
Command/Response Interpretation
CRI defines the end of the ISDN user-network interface the ISAC-S is used on, for
the correct identification of "Command" and "Response" frames. Depending on the
value of CRI the C/R-bit will be interpreted by the ISAC-S, when receiving frames in
auto-mode, as follows:
C/R Bit
Command
Receiving End
subscriber
network
Command
Response
0
1
1
0
0
1
For transmitting frames in auto-mode, the C/R-bit manipulation will also be done
automatically, depending on the value of the CRI-bit (refer to XAD1 register
description).
In message transfer modes with SAPI address recognition the first received address
byte is compared with the programmable values in SAP1, SAP2 and the fixed group
SAPI.
In 1-byte address mode, the CRI-bit is to be set to "0".
4.1.15 Receive Status Register
RSTA
Read
Address 27
H
Value after reset: undefined
7
0
RDA
RDO
CRC
RAB
SA1
SA0
C/R
TA
RDA
RDO
Receive Data
A "1" indicates that data is available in the RFIFO. After an RME interrupt, a "0" in this
bit means that data is available in the internal registers RHCR or SAPR only (e.g.
S-frame). See also RHCR register description table.
Receive Data Overflow
At least one byte of the frame has been lost, because it could not be stored in RFIFO
(1).
Semiconductor Group
212
INFINEON [ Infineon ]
