LM3S5C36 Datasheet, PDF (468/1068 Pages) Texas Instruments – Stellaris® LM3S5C36 Microcontroller

General-Purpose Timers
Table 10-5. 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, GPTM2
follows GPTM1, and so on. 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 10-2 on page 468 shows how the GPTMCFG bit
affects the daisy chain. This function is valid for both one-shot and periodic modes.
Figure 10-2. 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
10.3.2.2
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
Timer A Interval Load (GPTMTAILR) register (see page 497). Table 10-6 on page 468 shows the
values that are loaded into the timer registers when the timer is enabled.
Table 10-6. Counter Values When the Timer is Enabled in RTC Mode
Register
TnR
Count Down Mode
Not available
Count Up Mode
0x1
468
January 23, 2012
Texas Instruments-Production Data