LM3S5G31 Datasheet, PDF (555/1223 Pages) Texas Instruments – Stellaris LM3S5G31 Microcontroller

Stellaris^® LM3S5G31 Microcontroller
If the TnSTALL bit in the GPTMCTL register is set, the timer freezes counting while the processor
is halted by the debugger. The timer resumes counting when the processor resumes execution.
The following table shows a variety of configurations for a 16-bit free-running timer while using the
prescaler. All values assume an 80-MHz clock with Tc=12.5 ns (clock period). The prescaler can
only be used when a 16/32-bit timer is configured in 16-bit mode.
Table 11-6. 16-Bit Timer With Prescaler Configurations
Prescale (8-bit value)
# of Timer Clocks (Tc)^a
00000000
1
00000001
2
00000010
3
------------
--
11111101
254
11111110
255
11111111
256
a. Tc is the clock period.
Max Time
0.8192
1.6384
2.4576
--
208.0768
208.896
209.7152
Units
ms
ms
ms
--
ms
ms
ms
Wait-for-Trigger Mode
The Wait-for-Trigger mode allows daisy chaining of the timer modules such that once configured,
a single timer can initiate mulitple timing events using the Timer triggers. Wait-for-Trigger mode is
enabled by setting the TnWOT bit in the GPTMTnMR register. When the TnWOT bit is set, Timer N+1
does not begin counting until the timer in the previous position in the daisy chain (Timer N) reaches
its time-out event. The daisy chain is configured such that GPTM1 always follows GPTM0 and
GPTM2 follows GPTM1. If Timer A is in 32-bit mode (controlled by the GPTMCFG bit in the GPTMCFG
register), it triggers Timer A in the next module. If Timer A is in 16-bit mode, it triggers Timer B in
the same module, and Timer B triggers Timer A in the next module. Care must be taken that the
TAWOT bit is never set in GPTM0. Figure 11-2 on page 555 shows how the GPTMCFG bit affects the
daisy chain. This function is valid for both one-shot and periodic modes.
Figure 11-2. Timer Daisy Chain
GP Timer N+1
10
GPTMCFG
Timer B
Timer A
Timer B ADC Trigger
Timer A ADC Trigger
GP Timer N
10
GPTMCFG
Timer B
Timer A
Timer B ADC Trigger
Timer A ADC Trigger
11.3.2.2
Real-Time Clock Timer Mode
In Real-Time Clock (RTC) mode, the concatenated versions of the Timer A and Timer B registers
are configured as an up-counter. When RTC mode is selected for the first time after reset, the
counter is loaded with a value of 0x1. All subsequent load values must be written to the GPTM
July 03, 2014
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