User`s guide

6: BSC 2780/3780 Link Configuration Options
DC 900-1340I 175
6.18 Block Checking Option (20)
This option determines what characters are included in the block check character
(BCC) calculation on transmitted and received data blocks. If the received block check
character does not match the BCC value calculated by BSC, the
DLI_ICP_ERR_BAD_BCC
error code is returned to the client application. Block checking can be set to include or
exclude the leading BSC control character or can be disabled completely.
If the option is set to exclude, the BCC calculation starts with the first data character fol-
lowing STX. This is the normal BSC mode of BCC calculation.
If the option is set to include, the STX is included in the BCC calculation for transmitted
and received data blocks.
If the option is set to disable, a block check character is still generated on transmit and
expected on receive, but the receive BCC comparison is not performed and each
received data block is sent to the client without regard to any possible error. The BCC
calculation is done on transmitted blocks as if the option is set to exclude.
To set this option using the DLI configuration file, use the blockChecking parameter; for
example,
blockChecking = “exclFirst”. See Table 7–2 on page 191.
Note
When transmitting non-transparent text, embedded SYN charac-
ters are not included in the outbound BCC calculation.
6.19 Queue Limit Option (21)
The queue limit option is used to prevent the ICP message buffer pool from being
exhausted. Message buffers for all links on the ICP are taken from the same memory
pool. This method allows each link to draw buffers as demand increases. However, if a
process in the client were to stop reading on one link without disabling the link, incom-