Siemens SIMATIC S5 IP 281 Equipment Manual page 83

R 11192
When are Interrupts can be processed when the supply voltage of the module is
within the tolerance range, and the RESET signal is inactive ("0").
interrupts
acquired?
Incoming interrupts are not processed as long as the BASP signal is active
("l"),
When an interrupt is queued and the BASP signal becomes active, the inter-
rupt is removed by the 1P 281 from the S5 bus. The interrupt is output again
when the BASP signal becomes inactive again.
This behavior is not affected by plug–in jumper X20 (BASP selection)
Acknowledging When an interrupt is triggered by an interrupt enabled in interrupt enable
the interrupts register IFR (-+ section 3.6), the cause is entered in interrupt information
register HR.
Interrupts which are not enabled do not trigger an interrupt and are not en-
tered in the HR.
Reading the IIR causes the interrupt to be reset,
Although one byte in the HR is available to each counter (-+ section 3.7), the
of word commands LPW/LOW is recommended for the access.
When several interrupts occur before the IIR is read by the S5 CPU, these
are also entered in the IIR.
When interrupts arrive while the IIR is being read, these are stored inter-
mediately. An interrupt is then triggered again after the read procedure is
concluded.
2.3).
section
I
1
0
Startup or RESET:
Interrupts are deleted.
Interrupts are suppressed.
When the CPU 944A/B is used, byte commands must be used for
the access. While the IIR is being accessed with byte commands,
the interrupt processing must b= disabled with the S5 command
1A, and then enabled again with RA after the access.
Interrupt Processing
Interrupt Interrupts cannot
pass through.
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