Installation guide

44 DC 900-1564A
Synchronous Link Control (SLC) Programmer’s Guide
When the application writes a DLI_PROT_SEND_PRIOR_DATA command, the ICP uses the
iProtModifier field (AML value) to compute a corresponding message block identifier
for each information block transmitted. The application reads a
DLI_PROT_SAFE_STORE_ACK response when the ICP reports a corresponding acknowl-
edgment. If the
iICPStatus field value is DLI_ICP_CMD_STATUS_OK, receipt of a
DLI_PROT_SAFE_STORE_ACK response constitutes acknowledgment
3
that the specified
message has been stored safely at a remote site. If the
iICPStatus field value contains a
negative error code value, receipt of a
DLI_PROT_SAFE_STORE_ACK response constitutes a
failure in message transmission or a rejection of the specified message by the remote
site.
Table 5–18 on page 77 lists symbolic names for the
DLI_PROT_SEND_PRIOR_DATA AML
values that can appear in the
iProtModifier field for both writes and reads. The validity
of these values is influenced by both the network level and the message length. An AML
for a single-block message can be used only with a message that fits within a single
transmission block on the SLC network. However, an AML for a multi-block message
can be used for either a single-block message or a multi-block message.
The
DLI_PROT_SEND_PRIOR_DATA data content is variable. It contains selected SLC infor-
mation block header fields followed by the (optional) message information field. The
SLC protocol software supports a maximum message information field size of 4000
bytes for low-level network messages or 3840 bytes for high-level network messages.
For additional information on data content, see Section 6.4.2 on page 85 and
Section 6.4.3 on page 88.
3. In the case of messages sent with no protection indicated, DLI_PROT_SAFE_STORE_ACK reports trans-
mission success or failure.