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TC1796
Peripheral Units (Vol. 2 of 2)
General Purpose Timer Array (GPTA)
User’s Manual
24-231
V2.0, 2007-07
GPTA, V2.0
24.4.3
Interrupt Sharing Unit (IS)
The LTCA2 provides 16 service request sources. These service request sources are
generated by the LTCs.
To reduce hardware and software overhead, four request sources are combined
together in service request groups. A service request group y (y = 00-15) has four
service request inputs and one service request output SRy which is typically connected
outside the LTCA2 kernel to a standard interrupt node y and controlled by its SRCy
register.
Figure 24-84 Service Request Groups
The bits in the Service Request State Registers (SRSSx and SRSCx, x = 3, 2) are
service request status flags that are set by hardware (type “h”) when the related event
occurs. Each LTCA2 service request source has its own service request flag. This flag
is normally set by hardware but can be set and cleared by software. Each service request
status flag can be read twice, at the same bit location in SRSCx register and in SRSSx
register, and cleared or set by software when writing to the corresponding request bit in
SRSCx or SRSSx. When writing to SRSCx or SRSSx, several flags can be cleared at
once by one write operation. Flags written with 0 are not influenced. This feature allows
fast, simple clearing or setting of request flags without affecting other bits in the same
register.
Note that the service request flag is always set by the service request event even if the
corresponding service request is disabled in the interrupt node.
Table 24-21 LTCA2 Number of Service Request Sources
Cell Type
Number of Cells
Number of Service Request
Sources/Cell
Total Number of
Request Sources
LTC
64
1
16
MCA05993
At maximum
four Request
Sources
from LTCs
Service
Request
Node y
(SRCy Register)
Service Request
Group y
SRy
≥
1