User`s guide

92 DC 900-1340I
BSC Programmer’s Guide
When the EBCDIC/CRC-16 setting is used, the BSC control sequences are transmitted
in 8-bit EBCDIC, and the CRC-16 block check polynomial is used. The parity option is
ignored when using EBCDIC/CRC-16.
The BSC software transmits ASCII control characters on the line with space parity when
you select no parity (Section 4.6).
To set this option using the DLI configuration file, use the charSet parameter; for exam-
ple,
charSet = “asciilrc8”. See Table 7–1 on page 190.
4.8 Transmission Block Size Option (8)
The BSC software has transmission buffers fixed at 4,096 bytes. Each link has one trans-
mit buffer and one receive buffer. You can define the maximum amount of the 4,096
bytes that the BSC software can transmit as one block on the communication line by
setting the transmission block size from 64 to 4,096 bytes. The BSC software, however,
can receive blocks up to 4,096 bytes regardless of the setting of this option. See
Section 2.1.4 on page 35 for more information on transmission blocks.
The size of the transmission block includes the bisynchronous text control characters as
well as the data characters. For example, a transmission block size of 512 bytes consists
of 510 bytes of data plus two control characters (STX and ETX). SYN, DLE, PAD, and
BCC characters are not included in the transmission block size count. The BSC software
automatically inserts all control characters in the transmission block. If the remote sta-
tion sends a transmission block that is larger than 4,096 bytes, the BSC software sends a
NAK response to the transmission and returns the
DLI_ICP_ERR_BUF_OVERFLOW buffer
overrun error to the client along with all the data which was successfully received.
The size of message buffers from the client is independent of the transmission block
size. The ICP message buffer size is controlled by the Set ICP Message Buffer Size com-
mand (Section 3.4.1.3 on page 58). Messages to be transmitted that are greater than the
transmission block size are broken into smaller messages and sent separately.