Modes of Operation
8-12
ADSP-BF59x Blackfin Processor Hardware Reference
Once a timer has been enabled, the timer counter register is loaded with a
starting value. If
CLK_SEL
= 0, the timer counter starts at 0x1. If
CLK_SEL
= 1, it is reset to 0x0 as in
EXT_CLK
mode. The timer counts
upward to the value of the timer period register. For either setting of
CLK_SEL
, when the timer counter equals the timer period, the timer coun-
ter is reset to 0x1 on the next clock.
In
PWM_OUT
mode, the
PERIOD_CNT
bit controls whether the timer generates
one pulse or many pulses. When
PERIOD_CNT
is cleared (
PWM_OUT
single
pulse mode), the timer uses the
TIMER_WIDTH
register, generates one assert-
ing and one deasserting edge, then generates an interrupt (if enabled) and
stops. When
PERIOD_CNT
is set (
PWM_OUT
continuous pulse mode), the
timer uses both the
TIMER_PERIOD
and
TIMER_WIDTH
registers and generates
a repeating (and possibly modulated) waveform. It generates an interrupt
(if enabled) at the end of each period and stops only after it is disabled. A
setting of
PERIOD_CNT
= 0 counts to the end of the width; a setting of
PERIOD_CNT
= 1 counts to the end of the period.
The
TIMER_PERIOD
and
TIMER_WIDTH
registers are read-only in some
operation modes. Be sure to set the
TMODE
field in the
TIMER_CONFIG
register to b#01 before writing to these registers.
Output Pad Disable
The output pin can be disabled in
PWM_OUT
mode by setting the
OUT_DIS
bit in the
TIMER_CONFIG
register. The
TMR
pin is then three-stated regard-
less of the setting of
PULSE_HI
and
TOGGLE_HI
. This can reduce power
consumption when the output signal is not being used. The
TMR
pin can
also be disabled by the function enable and the multiplexer control
registers.
Single Pulse Generation
If the
PERIOD_CNT
bit is cleared, the
PWM_OUT
mode generates a single pulse
on the
TMR
pin. This mode can also be used to implement a precise delay.
Summary of Contents for ADSP-BF59x Blackfin
Page 64: ...Development Tools 1 22 ADSP BF59x Blackfin Processor Hardware Reference...
Page 74: ...Processor Specific MMRs 2 10 ADSP BF59x Blackfin Processor Hardware Reference...
Page 244: ...Programming Examples 6 40 ADSP BF59x Blackfin Processor Hardware Reference...
Page 700: ...Programming Examples 16 78 ADSP BF59x Blackfin Processor Hardware Reference...
Page 738: ...Boundary Scan Architecture B 8 ADSP BF59x Blackfin Processor Hardware Reference...