ADSP-BF537 Blackfin Processor Hardware Reference
15-35
General-Purpose Timers
The timer works as a counter clocked by an external source, which can
also be asynchronous to the system clock. The current count in
TIMERx_COUNTER
represents the number of leading edge events detected.
Setting the
TMODE
field to b#11 in the
TIMERx_CONFIG
register enables this
mode. The
TIMERx_PERIOD
register is programmed with the value of the
maximum timer external count.
The waveform applied to the
TMRx
pin is not required to have a 50% duty
cycle, but the minimum
TMRx
low time is one
SCLK
period, and the mini-
mum
TMRx
high time is one
SCLK
period. This implies the maximum
TMRx
input frequency is
SCLK/2
.
Period may be programmed to any value from 1 to (2
32
– 1), inclusive.
After the timer has been enabled, it resets the timer counter register to 0x0
and then waits for the first leading edge on the
TMRx
pin. This edge causes
the timer counter register to be incremented to the value 0x1. Every
Figure 15-16. Timer Flow Diagram, EXT_CLK Mode
CLOCK
RESET
LEADING
EDGE
DETECT
TIMERx_COUNTER
TIMERx_PERIOD
TIMER_ENABLE
INTERRUPT
EQUAL?
Y
PULSE_HI
TMRx
DATA BUS
Summary of Contents for Blackfin ADSP-BF537
Page 42: ...Contents xlii ADSP BF537 Blackfin Processor Hardware Reference ...
Page 90: ...Development Tools 1 32 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 138: ...Programming Examples 4 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 340: ...SDC Programming Examples 6 84 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 606: ...Programming Examples 9 94 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 660: ...Programming Examples 10 54 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 720: ...Electrical Specifications 11 60 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 840: ...Programming Examples 13 42 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 876: ...Programming Examples 14 36 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 938: ...Programming Examples 15 62 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 958: ...Programming Examples 17 12 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 986: ...Programming Examples 18 28 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 1162: ...G 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 1218: ...Index I 56 ADSP BF537 Blackfin Processor Hardware Reference ...