
Description of Operation
8-4
ADSP-BF59x Blackfin Processor Hardware Reference
Clock and capture input pins are sampled every
SCLK
cycle. The duration
of every low or high state must be at least one
SCLK
. Therefore, the maxi-
mum allowed frequency of timer input signals is
SCLK
/
2
.
Internal Interface
Timer registers are always accessed by the core through the 16-bit PAB
bus. Hardware ensures that all read and write operations from and to
32-bit timer registers are atomic.
Every timer has a dedicated interrupt request output that connects to the
system interrupt controller (SIC).
Description of Operation
The core of every timer is a 32-bit counter, that can be interrogated
through the read-only
TIMER_COUNTER
register. Depending on the mode of
operation, the counter is reset to either 0x0000 0000 or 0x0000 0001
when the timer is enabled. The counter always counts upward. Usually, it
is clocked by
SCLK
. In PWM mode it can be clocked by the alternate clock
input
TACLK
or, alternatively, the common timer clock input
TMRCLK
. In
counter mode, the counter is clocked by edges on the
TMR
input pin. The
significant edge is programmable.
After 2
32
-1 clocks, the counter overflows. This is reported by the over-
flow/error bit
TOVF_ERR
in the
TIMER_STATUS
register. In PWM and
counter mode, the counter is reset by hardware when its content reaches
the values stored in the
TIMER_PERIOD
register. In capture mode, the coun-
ter is reset by leading edges on the
TMR
or
TACI
input pin. If enabled, these
events cause the interrupt latch
TIMIL
in the
TIMER_STATUS
register to be
set and issue a system interrupt request. The
TOVF_ERR
and
TIMIL
latches
are sticky and should be cleared by software using W1C (write-1-to-clear)
operations to clear the interrupt request. The global
TIMER_STATUS
register
Содержание ADSP-BF59x Blackfin
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