Reference Guide

ZCOM Tables and Data Structures
ZLU Tables
Chapter 360
ZCKSUM - ZLU checksum
The checksum is used as an integrity check to ensure that a ZLU has not
been altered while it is active. It is the 16-bit binary sum of bytes 3 to 18
of the ZLU entry (with any overflow discarded). It is calculated when the
ZLU table entry is created.
ZLTYPE - Type of ZLU
The ZLU type values are shown in Table 3-8. The type value is also used
to indicate whether the ZLU is defined.
* The logical terminal number is allocated by TTGEN from the TTGEN
configuration file.
ZPOINT - ZLU pointer or mapped node number
The field is used to link the ZLU with the entity it represents. The
meaning of the field is given in the table under ZLTYPE.
ZMPZLU - Mapped ZLU number
If the ZLU is type 3 (mapped ZLU), then this is the ZLU number (on the
node as given by ZPOINT) onto which this ZLU is being mapped. If ZLU
is not type 3, ZMPZLU is set to zero.
ZMPZCS - Mapped ZLU checksum
spare1 Reserved, not used int 4
Table 3-7 Individual ZLU Data Structure (zlu_type) (Continued)
Field Name Field Description Field Type
Size
(Bytes)
Table 3-8 ZLU Type Values
Type Description
0 ZLU is not defined
1 ZLU is local terminal (ZPOINT is a logical terminal number *)
2 ZLU is a local program (ZPOINT is a queue number)
3 ZLU is mapped (ZPOINT is a mapped ZLU node number)