
PSB 7115
Functional Description
Semiconductor Group
43
02.98
Path 1
is used to access the fax/modem engine, a V.110 formatter, a DTMF generator/
detector or for transparent access to the IOM-2 timeslots.
Path 2
is used to access a V.110 formatter or it provides transparent access to the IOM-
2 timeslots. This datapath must not be configured to V.110 if path 1 is configured to
datamodem modulations at the same time.
Path 1 and 2
integrate a SART (Synchronous Asynchronous Receiver Transmitter)
which supports ASYNC, HDLC and binary mode. In ASYNC mode, the characters are
formatted according to the ITU-T V.14 standard by start, parity and stop bits. In HDLC
mode, the HDLC bit level functions (Flag, CRC, Zero-bit handling) are performed. Binary
mode describes a synchronous, transparent mode without formatting.
Path 3
incorporates an HDLC controller for D-channel data transfer and handles the
access to the C/I-channel. The ISAR 34 supports the TIC bus arbitration mechanism for
those applications where several controllers are connected to the IOM-2 interface.
Path 4
provides a MONITOR channel handler for information exchange with other
devices. Messages for test and diagnostics purposes are also transferred via this
datapath.
2.5.1
The mailbox represents the common host interface for all data paths, which are the two
B-Channel paths, the D- and C/I-channel path and the MONITOR channel and test/
diagnostics path. For each data path the read and write direction is buffered with a FIFO
(see
figure 22
).
The complete buffer size for one data path is 2x256 byte (path 1, 2 and 3) or 2x64 byte
(path 0) per direction. Since the interrupt status byte and the control word is also
transferred to the buffer by the ISAR 34, the available FIFO space for user data is
reduced by 3 bytes. So messages may contain a maximum number of user data of 253
or 61 byte, respectively.
The maximum possible message length MPL for each path is shown in
table 4
. DPS is
the Data Path Select parameter in the Host/ISAR Interrupt status byte (HIS/IIS) of each
message.
Table 4
Buffer size
DPS
Buffer
MPL
Buffer Size
(per direction)
2 x 64 byte
2 x 256 byte
2 x 256 byte
2 x 256 byte
Datapath 0
Datapath 1
Datapath 2
Datapath 3
0 0
0 1
1 0
1 1
61 byte
253 byte
253 byte
253 byte