User`s guide

5: BSC 2780/3780 DLI Functions
DC 900-1340I 149
The BSC 2780/3780 software transmits the data in the modified format of Figure 5–5:
The DLE characters are not counted in the transmission block size. The BSC 2780/3780
software performs all the required SYN, DLE, STX, ETB, ETX, US, and CRC insertion
and deletion for transparent 2780 data streams.
5.4.3.4 Priority Data
Use the dlWrite function with the pOptArgs.usProtCommand field set to
DLI_PROT_SEND_PRIOR_DATA or DLI_PROT_SEND_PRIOR_DATA_EOM to send priority data. When
the client computer sends non-transparent priority data to the BSC 2780/3780 soft-
ware, the software transmits the data immediately if the link is idle. If the link is cur-
rently receiving data, the BSC 2780/3780 software sends a reverse interrupt (RVI) to
request a line turnaround in order to transmit the priority message. After the remote
station turns the line around, the BSC 2780/3780 software sends the priority message.
Non-transparent priority data blocks received from the line are reported to the client as
normal data (the
dlRead pOptArgs.usProtCommand field is set to
DLI_PROT_SEND_NORM_DATA or DLI_PROT_SEND_NORM_DATA_EOM).
5.4.3.5 Header Data
Use the dlWrite function with the pOptArgs.usProtCommand field set to
DLI_PROT_SEND_HDR_DATA or DLI_PROT_SEND_HDR_DATA_EOM to send header data. The client
uses the header data commands for transmitting non-transparent data that starts with
the SOH character on the line. Non-transparent header data blocks received from the
line are also reported by the BSC 2780/3780 software to the client as normal data (the
dlRead pOptArgs.usProtCommand field is set to DLI_PROT_SEND_NORM_DATA or
DLI_PROT_SEND_NORM_DATA_EOM).
Figure 5–5: BSC 2780/3780 Modified Transparent 2780 Record Format
SYN SYN DLE STX record 1 DLE US CRC SYN SYN DLE STX record 2
DLE US CRC … SYN SYN DLE STX record n DLE ETB CRC