Purpose
Provide
generic data link control (GDLC) with data types, service access points
(SAPs), and link station (LS) correlators.
Description
An extended write or writex subroutine
must be issued by an application or kernel user to provide GDLC with
data types, SAPs, and LS correlators.
These
DLC extended parameters for the write subroutine are part of
the data link control in BOS Extensions 2 for the device manager you
are using.
Parameters
| Item |
Description |
|---|
| sap_corr |
Specifies the GDLC SAP correlator of the write data. This
field must contain the same correlator value passed back form GDLC
in the gdlc_sap_corr field when the SAP was enabled. |
| dlh_len |
Not used for writes. |
| ls_corr |
Specifies the GDLC LS correlator of the write data. This
field must contain the same correlator value passed back from GDLC
in the gdlc_ls_corr field when the LS was started. |
| flags |
Specifies flags for the writex subroutine. The following
flags are supported: - DLC_INFO
- Requests a sequenced data class of information to be sent (generally
called I-frames).
This request is valid any time the target link
station has been started and contacted.
- DLC_XIDD
- Requests an exchange identification (XID) non-sequenced command
or response packet to be sent.
This request is valid any time
the target link station has been started with the following rules:
GDLC
sends the XID as a command as long as no DLC_TEST, DLC_CONTACT, DLC_HALT_LS,
or DLC_XIDD write subroutine is already in progress, and no
received XID is waiting for a response. If a received XID is waiting
for a response, GDLC automatically sends the write XID as that response.
If no response is pending and a command is already in progress, the
write is rejected by GDLC.
- DLC_DGRM
- Requests a datagram packet to be sent. A datagram is an unnumbered
information (UI) response.
This request is valid any time the
target link station has been started.
- DLC_NETD
- Requests that network data be sent.
Examples of network
data include special modem control data or user-generated medium access
control (MAC) and logical link control (LLC) headers.
Network
data must contain the entire MAC layer packet headers so that the
packet can be sent without the data link control (DLC)'s intervention.
GDLC only provides a pass-through function for this type of write.
This
request is valid any time the SAP is open.
|