Copyright © Siemens AG 2016. All rights reserved
59
ERTEC 200P-2 Manual
Technical data subject to change
Version 1.0
If more than one bit is set in the ISREG because during the currently running interrupt
process interrupts with higher priority have occurred, the EOI command clears the bit that
belongs to the currently processed interrupt with the highest priority.
To ensure that the entry in the ISREG with the highest priority matches the interrupt for
which the last acknowledge was issued (i.e. that currently being processed by the CPU),
the assignment of the priorities may no longer be changed after an acknowledge.
The ICU considers the interrupt processing to have finished completely when all bits in
the ISREG have been cleared. When the last bit has been cleared in the ISREG, all inter-
rupts with lower priority that have been entered in the Interrupt Request register in the
meantime will also be further processed.
2.3.2.11
Special functions
The ICU permits the additional confirmation of an interrupt by any write access to the
INTB_ACK/INTA_ACK register. This function is deactivated after reset and must be acti-
vated prior to use with the INTB_UNLOCK_READ_ONLY register bit (for each INTA/INTB
block seperately).
This acknowledge using write access is destructive. This means the vector number of the
confirmed interrupt then cannot be fetched using the ACK or the IVEC register. Conse-
quently, this function must be enabled prior to its use.
As an additional special function, there is an ID register that contains the implemented
version number of the ICU. The software can read this version number.
The ICU contains an ID register that contains the currently implemented version number
of the IP. The software can fetch this version number. Each subblock (INTB/INTA) has its
own version register. The ICU ID can be obtained from the register descriptions.
2.3.2.12
Debug functions
The CPU can fetch the vector number of the currently pending interrupt on the CPU with-
out confirming it. For this purpose, the vector number can be fetched using two different
addresses, one of which performs the acknowledge with the read access and the other is
provided only for debug purposes.
An interrupt that was reported to the CPU using the INTA or INTB signal is acknowledged
with a read access to the interrupt vector register (INTA_ACK or INTB_ACK). Because
this access is destructive, namely, the vector number can no longer be read after the
acknowledge, the additional address allows the vector to be fetched for debug purposes
without initiating any further processing.
The ICU has an input 'Debug acknowledge' (e.g. coming from the ARM9-Core in previous
designs) that can act directly on the global mask bit. This procedure can be enabled and
disabled using the MASK_ALL_INPUT_EN software register. The input is synchronized
by the ICU with a double flop.
In ERTEC 200P this input is tied inactive.
2.3.2.13
Miscellaneous
2.3.2.13.1 Synchronizing the inputs
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