SNAX/APN Application Programming Manual

The CRT Interface
SNAX/APN Application Programming Manual—420111-001
2-11
Setting and Fetching BREAK Parameters
(SETPARAM Function 3)
BREAK function and BREAK handling are described in greater detail in the Guardian
Programmer’s Guide.
Setting and Fetching BREAK Parameters (SETPARAM Function 3)
SETPARAM function 3 does three things:
•
Set BREAK functions (like SETMODE function 11)
•
Fetches current BREAK parameter values
•
Sets a BREAK tag that supports applications that own BREAK on multiple
subvolumes, allowing them to distinguish between break messages received from
different subdevices
SETPARAM function 3 has the following syntax:
param-array and last-param-array are both 8-byte integer arrays containing:
array[0] The equivalent of param1 in SETMODE function 11.
array[1] The equivalent of param2 in SETMODE function 11.
array[2] The most significant word (high word) in the BREAK tag.
array[3] The least significant word (low word) in the BREAK tag.
array[2] and array[3] together form the 32-bit BREAK tag.
last-params
allows you to view the most recent option setting. Because the option can also be
set using SCF or SPI, the returned value indicates the setting before this call takes
effect.
When a terminal user presses the BREAK key, an equivalent break-on-device system
message containing the BREAK tag is sent to the owner of BREAK. The message,
sysmsg, is composed of an array of words as follows:
sysmsg[0] -105, indicating that it is a break-on-device system message.
sysmsg[1] File number of the receiver’s open file to the device that indicated
break (or -1 if unavailable). The device must be open.
sysmsg[2,3] The 32-bit BREAK tag value.
CALL SETPARAM ( filenum , 3 [ , param-array , 8
[ , last-param-array , 8 ] ] ) ;