Texas Instruments SimpleLink CC2620 Technical Reference Manual page 1083

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(GPT:IMR), the GPTM also sets the GPTM Masked Interrupt Status Register (GPT:MIS) CnEMIS bit. In
this mode, the GPT:TnR register holds the time at which the selected input event occurred, while the
GPT:TnV and the GPT:TnPV registers hold the free-running timer value and the free-running prescaler
value. These registers can be read to determine the time that elapsed between the interrupt assertion and
the entry into the ISR.
In addition to generating interrupts a μDMA trigger can be generated. This trigger is enabled by
configuring and enabling the appropriate μDMA channel.
After an event has been captured, the timer does not stop counting. The timer continues to count until the
TnEN bit is cleared. When the timer reaches the timeout value, it is reloaded with 0x0 in up-count mode,
and the value from the GPT:TnILR and the GPT:TnPR registers in down-count mode.
Figure 13-3 shows how input edge timing mode works. In the diagram, it is assumed that the start value of
the timer is the default value of 0xFFFF, and the timer is configured to capture rising-edge events.
Each time a rising-edge event is detected, the current count value is loaded into the GPTIMER:TnR
register, and is held there until another rising edge is detected (at which point the new count value is
loaded into the GPT:TnR register).
0xFFFF
Input Signal
NOTE: When operating in edge-time mode, the counter uses a modulo 2
enabled, or 2
than the count, another timer can be used to ensure detection of the missed edge.
13.3.2.4 PWM Mode
The GPTM supports a simple PWM generation mode. In PWM mode, the timer is configured as a 16-bit
down counter with a start value (and thus, period) defined by the GPT:TnILR and the GPT:TnPR registers.
In this mode, the PWM frequency and period are synchronous events; therefore, they are ensured to be
glitch-free. PWM mode is enabled with the GPT:TnMR register by setting the TnAMS bit to 0x1, setting the
TnCM bit to 0x0, and setting the TnMR field to 0x2.
timer registers when the timer is enabled.
NOTE: Wait on trigger (daisy chaining) is not supported in PWM mode. The timer starts as soon as
it is enabled and does not wait for a trigger from the previous timer.
SWCU117C – February 2015 – Revised September 2015
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Figure 13-3. Input Edge-time Mode Example
Count
GPTMTnR=X
Z
X
Y
16
if prescaler is not enabled. If there is a possibility the edge could take longer
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GPTMTnR=Y
24
count if prescaler is
Table 13-5 lists the values that are loaded into the
Functional Description
GPTMTnR=Z
Time
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Timers