LM3S6611-IQC20-A0T ETC2 [List of Unclassifed Manufacturers], LM3S6611-IQC20-A0T Datasheet - Page 200

• Manufacturer Part Number: LM3S6611-IQC20-A0T
• Description: Microcontroller
• Manufacturer: ETC2 [List of Unclassifed Manufacturers]

General-Purpose Timers
10.2.3.3 16-Bit Input Edge Time Mode
200
Figure 10-2. 16-Bit Input Edge Count Mode Example
Note:
In Edge Time mode, the timer is configured as a free-running down-counter initialized to the value
loaded in the GPTMTnILR register (or 0xFFFF at reset). This mode allows for event capture of both
rising and falling edges. The timer is placed into Edge Time mode by setting the TnCMR bit in the
GPTMTnMR register, and the type of event that the timer captures is determined by the TnEVENT
fields of the GPTMCnTL register.
When software writes the TnEN bit in the GPTMCTL register, the timer is enabled for event capture.
When the selected input event is detected, the current Tn counter value is captured in the GPTMTnR
register and is available to be read by the controller. The GPTM then asserts the CnERIS bit (and
the CnEMIS bit, if the interrupt is not masked).
After an event has been captured, the timer does not stop counting. It continues to count until the
TnEN bit is cleared. When the timer reaches the 0x0000 state, it is reloaded with the value from the
GPTMnILR register.
Figure 10-3 on page 201 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 GPTMTnR
register, and is held there until another rising edge is detected (at which point the new count value
is loaded into GPTMTnR).
The prescaler is not available in 16-Bit Input Edge Time mode.
Input Signal
0x000A
0x0009
0x0008
0x0007
0x0006
Count
Preliminary
on next cycle
Timer reload
Timer stops,
asserted
flags
October 09, 2007
Ignored
Ignored