ACC Programmer's Reference Guide

58 Chapter3
ZCOM Tables and Data Structures
ZLU Tables
ZCKSUM -ZLUchecksum
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 tabl e entry is created.
ZLTYPE -TypeofZLU
TheZLUtypevaluesareshowninTable3-8.Thetypevalueisalsoused
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 i n 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 -MappedZLUchecksum
If the ZLU is not type 3, ZMPZCS is set to zero. Otherwise, this contains
the checksum of the mapped ZLU.
ZLNAME -NameofZLU
Name assigned to the ZLU by the creator of the ZLU. If the ZLU is the
input queue to a program then this name i s usually Z99999 - where
99999 is the program PID number. In this case the other 2 bytes are
space filled. The program ZLU name can be assigned by t he zopen call
when the ZLU is allocated. The ZLU name can be found using zinfo given
Table3-8 ZLUTypeValues
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)