ADSP-BF535 Blackfin Processor Hardware Reference
16-21
Timers
External Event Counter Mode (EXT_CLK)
In EXT_CLK mode, the
TMRx
pin is an input. The timer works as a coun-
ter clocked by any external source, which can also be asynchronous to the
core clock. Setting the
MODE_FIELD
bits in
TIMERx_CONFIG
to b#11 enables
this mode. The
TIMERx_PERIOD
register is programmed with the value of
the maximum timer external count.
After the timer is enabled, it waits for the first rising edge on the
TMRx
pin.
This edge forces the Timer Count register to be loaded by the value
(0xFFFF FFFF – period). Every subsequent rising edge increments the
count register. After reaching the count value 0xFFFF FFFE, the
IRQx
bit
is set and an interrupt is generated. The next rising edge reloads the count
register again by (0xFFFF FFFF – period).
The
PULSE_HI
and the
PERIOD_CNT
configuration bits have no effect in this
mode, and the
OVF_ERRx
bits are never set. The Timer Width register is
not used.
Core Timer
The core timer is a programmable interval timer which can generate peri-
odic interrupts. The core timer runs at the core clock (
CCLK
) rate. The
timer includes four core MMRs, the Timer Control register (
TCNTL
), the
Timer Count register (
TCOUNT
), the Timer Period register (
TPERIOD
), and
the Timer Scale register (
TSCALE
).
Figure 16-13
provides a block diagram of the core timer.
Summary of Contents for ADSP-BF535 Blackfin
Page 80: ...Development Tools 1 26 ADSP BF535 Blackfin Processor Hardware Reference...
Page 312: ...Working With Memory 6 86 ADSP BF535 Blackfin Processor Hardware Reference...
Page 332: ...System Interfaces 7 20 ADSP BF535 Blackfin Processor Hardware Reference...
Page 360: ...Dynamic Power Management Controller 8 28 ADSP BF535 Blackfin Processor Hardware Reference...
Page 446: ...Beginning and Ending an SPI Transfer 10 40 ADSP BF535 Blackfin Processor Hardware Reference...
Page 522: ...Timing Examples 11 76 ADSP BF535 Blackfin Processor Hardware Reference...
Page 562: ...IrDA Support 12 40 ADSP BF535 Blackfin Processor Hardware Reference...
Page 608: ...PCI I O Issues 13 46 ADSP BF535 Blackfin Processor Hardware Reference...
Page 672: ...References 14 64 ADSP BF535 Blackfin Processor Hardware Reference...
Page 810: ...SDRAM Controller SDC 18 86 ADSP BF535 Blackfin Processor Hardware Reference...
Page 811: ...ADSP BF535 Blackfin Processor Hardware Reference 18 87 External Bus Interface Unit...
Page 812: ...SDRAM Controller SDC 18 88 ADSP BF535 Blackfin Processor Hardware Reference...
Page 860: ...DMA Bus Debug Registers 20 30 ADSP BF535 Blackfin Processor Hardware Reference...