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Description of Operation
8-44
ADSP-BF537 Blackfin Processor Hardware Reference
conclusion of each frame. The counters may be read at any time, but may
not be written. The counters can be reset to zero all at once by writing the
RSTC
bit to 1.
The counters can be configured to be cleared individually after each read
access if the
CCOR
bit is set to 1. This mode guarantees that no counts are
dropped between the value returned by the read and the value remaining
in the register.
L
Although this read operation has a side effect, the speculative read
operation of the Blackfin core pipeline is properly handled by the
MAC. During the time between the speculative read stage and the
commit stage of the read instruction, the MMC block freezes the
addressed counter so that intervening updates are deferred until the
MMR read instruction is resolved.
For best results, to minimize the amount of time that any given
MMC counter is frozen, it is suggested not to intentionally place
MMC counter read instructions in positions that result in frequent
speculative reads which are not ultimately executed. For example,
MMC counter reads should not be placed in the shadow of fre-
quently-mispredicted flow-of-control operations.
a
Continuous polling of any MMC register is not recommended.
The MMC update process requires at least one
SCLK
cycle between
successive reads to the same register, which may not occur if the
register read is placed in a tight code loop. If the polling operation
excludes the MMC update process, loss of information results.
The overflow behavior of the counters is configurable using the
CROLL
bit.
The counters may be configured either to saturate at maximum value
(
CROLL
=
0
) or to roll over to zero and continue counting (
CROLL
=
1
).
The range of the counters can be extended into software-managed
counters (for example, 64-bit counters) by use of selectable MMC inter-
rupts. The
EMAC_MMC_RIRQE
and
EMAC_MMC_TIRQE
MMC interrupt enable
registers allow the programmer to select which counters should signal an
Содержание Blackfin ADSP-BF537
Страница 42: ...Contents xlii ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 90: ...Development Tools 1 32 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 138: ...Programming Examples 4 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 340: ...SDC Programming Examples 6 84 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 606: ...Programming Examples 9 94 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 660: ...Programming Examples 10 54 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 720: ...Electrical Specifications 11 60 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 840: ...Programming Examples 13 42 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 876: ...Programming Examples 14 36 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 938: ...Programming Examples 15 62 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 958: ...Programming Examples 17 12 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 986: ...Programming Examples 18 28 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 1162: ...G 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 1218: ...Index I 56 ADSP BF537 Blackfin Processor Hardware Reference ...