PAM Programming Manual

Link-Level Interfaces
PAM Programming Manual—142482
3-11
Formatting an SDU Header (Ethernet)
Formatting an SDU Header (Ethernet)
This primitive formats an individual SDU header within a previously created aggregate
SDU buffer. The SDU header begins at the first word boundary after the aggregate SDU
header, or the first word boundary after the preceding SDU, if any. This primitive passes
back to the application a byte offset from the beginning of the aggregate SDU buffer
indicating where the user data, if any, begins.
The syntax for this primitive is
The parameters for this primitive are defined as follows:
Aggr^SDU^Buff^ptr (STRING .EXT)
Required input used to reference the buffer to be used for the aggregate SDU to the
L2S Formatting Library.
L2S^Type (INT)
Required input (Port^Type value) that is used to determine how link service access
points (LSAPs) are interpreted and what type of SDU header to generate. Currently
defined values for this parameter are:
ZPAM^Val^Port^Type^Enet (DIX Ethernet, not IEEE 802.3)
ZPAM^Val^Port^Type^LLC1
For backward compatibility with TLAM applications these literals have the same
value as
ZLAM^Val^Port^Type^Enet and ZLAM^Val^Port^Type^LLC1.
L2S^SDU^Type (INT)
The ZL2S^Val^SDUType identifier is a required input that declares the kind of SDU
the application wishes to generate. The valid values for this parameter are:
ZL2S^Val^SDUType^UI
ZL2S^Val^SDUType^Test
ZL2S^Val^SDUType^XID
The Ethernet Port^Type supports only the UI SDUType. The LLC1 Port^Type
supports all three SDUTypes.
INT PROC ZL2S^Frmt^SDU^Hdr^
( Aggr^SDU^Buff^ptr
,L2S^Type
,L2S^SDU^Type
,P^F^Flag
,Rsp^Flag
,Foreign^Addr^ptr
,SDU^User^Data^Offset^B
,SDU^User^Data^Size^B
,Service^Class ) EXTENSIBLE;