HNDINT, HNDSVC 3. You are responsible for establishing proper entry and exit linkage
for your interruption handling routine. When your routine receives
control, the significant registers contain: 0-1 2-3 4 14 15
contents I/o-oIdPSW Channel status word (CSW) Address of interrupting device
Return address
Entry point address Your routine must return control to the address in 14, and
indicate, via register 15, whether processing is complete. A 0 in
register 15 means that you are through handling the interruption; any nonzero return code indicates that you expect another
interruption.
4. The interruption handling routine that you code should not perform any I/O operations. When it is given control, all IIO interruptions and external interruptions are disabled.
If an error condition occurs, register 15 will contain one of the
following return codes: Invalid device address (cuu) or interruption handling routine
address (addr).
2 Trap item replaces another of same device name.
3 Attempting to clear a nonexisting interruption.
HNDSVC Use the HNDSVC macro
specific supervisor call
macro instruction is:
instruction to trap (SVC) instructions.
interruptions caused by
The format of the HNDSVC r -----, I [label] I {
SET, (svcnum,. address) [ ,. (svcnum, address) ••• ] } I CLR,.svcnum[,.svcnum .•• ] , HNDSVC I , I [ , ERROR=erraddr] I L- label is an optional statement label. specifies that you want to trap SVcs of the specified
nu mber (s) .
sv cnum
address
specifies the number of the SVC you want to trap. SVC numbers
o through 200 and 206 through 255 are valid.
specifies the address of the routine in your program that
should receive control whenever the specified SVC is issued.
Section 6. Instructions 317

HNDSVC Macro CLR specifies that you no lonqer want to trap the specified SVC(s) • ERROR=eI:'raddr specifies the address of an error routine to be given control
if an error is found. If ERROR= is not coded and an error
occurs, control returns to the next sequential instruction in
the calling program, as it does if no error occurs. You responsible for providing the proper entry and exit linkage for YOUI:' routine. When your program receives control, the
register contents are as follows: contents
12 Address-of your SYC-handling routine
13 Address of an 18-fullword save area (for your use) 14 Return address Yoar routine must return control to the address in register 14. If an eI:'roI:' occurs, register 15 contains one of the following eI:'ror codes: !1gggiRS Invalid SVC number or address SVC number set replaced previously set number SVC number cleared was not set
318 IBM YM/370 CMS Command and Macro Reference