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Functional Description
1267
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
General-Purpose Timers
18.3.6 DMA Operation
The timers each have a dedicated µDMA channel and can provide a request signal to the µDMA
controller. Pulse requests are generated by a timer via its own dma_req signal. A dma_done signal is
provided from the µDMA to each timer to indicate transfer completion and trigger a µDMA done interrupt
(DMAnRIS) in the GPTM Raw Interrupt Status Register (GPTMRIS) register. The request is a burst type
and occurs whenever a timer raw interrupt condition occurs. The arbitration size of the µDMA transfer
should be set to the amount of data that should be transferred whenever a timer event occurs.
For example, to transfer 256 items, 8 items at a time every 10 ms, configure a timer to generate a periodic
time-out at 10 ms. Configure the µDMA transfer for a total of 256 items, with a burst size of 8 items. Each
time the timer times out, the µDMA controller transfers 8 items, until all 256 items have been transferred.
See
for more details about programming the µDMA controller.
A GPTM DMA Event (GPTMDMAEV) register is provided to enable the types of events that can cause a
dma_req signal assertion by the timer module. Application software can enable a dma_req trigger for a
match, capture or time-out event for each timer using the GPTMDMAEV register. For an individual timer,
all active timer trigger events that have been enabled through the GPTMDMAEV register are ORed
together to create a single dma_req pulse that is sent to the µDMA. When the µDMA transfer has
completed, a dma_done signal is sent to the timer resulting in a DMAnRIS bit set in the GPTMRIS
register.
18.3.7 ADC Operation
The timer has the capability to trigger the ADC when the TnOTE bit is set in the GPTMCTL register at
offset 0x00C. The GPTM ADC Event (GPTMADCEV) register is additionally provided so that the type of
ADC trigger can be defined. For example, by setting the CBMADCEN bit in the GPTMADCEV register, a
trigger pulse will be sent to the ADC whenever a Capture Match event occurs in GPTM B. Similar to the
µDMA operation, all active trigger events that have also been enabled in the GPTMADCEV register are
ORed together to create an ADC trigger pulse.
18.3.8 Accessing Concatenated 16- or 32-Bit GPTM Register Values
The GPTM is placed into concatenated mode by writing 0x0 or 0x1 to the GPTMCFG bit field in the GPTM
Configuration (GPTMCFG) register. In both configurations, certain 16- or 32-bit GPTM registers are
concatenated to form pseudo 32-bit registers. These registers include the following:
•
GPTM Timer A Interval Load (GPTMTAILR) register [15:0], see
•
GPTM Timer B Interval Load (GPTMTBILR) register [15:0], see
•
GPTM Timer A (GPTMTAR) register [15:0], see
•
GPTM Timer B (GPTMTBR) register [15:0], see
•
GPTM Timer A Value (GPTMTAV) register [15:0], see
•
GPTM Timer B Value (GPTMTBV) register [15:0], see
•
GPTM Timer A Match (GPTMTAMATCHR) register [15:0], see
•
GPTM Timer B Match (GPTMTBMATCHR) register [15:0], see
In the 32-bit modes, the GPTM translates a 32-bit write access to GPTMTAILR into a write access to both
GPTMTAILR and GPTMTBILR. The resulting word ordering for such a write operation is:
GPTMTBILR[15:0]:GPTMTAILR[15:0].
Likewise, a 32-bit read access to GPTMTAR returns the value:
GPTMTBR[15:0]:GPTMTAR[15:0].
A 32-bit read access to GPTMTAV returns the value:
GPTMTBV[15:0]:GPTMTAV[15:0].