Preliminary
Introduction
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17.1 Introduction
17.1.1 Overview
The timer module contains a free running upward counter with auto reload capability on overflow. The
timer counter can be read and written in real-time (while counting). The timer module includes compare
logic to allow an interrupt event on a programmable counter matching value.
A dedicated output signal can be pulsed or toggled on overflow and match event. This output offers a
timing stamp trigger signal or PWM (pulse-width modulation) signal sources. A dedicated output signal
can be used for general purpose PORGPOCFG (directly driven by bit 14 of the TCLR register). A
dedicated input signal is used to trigger automatic timer counter capture and interrupt event, on
programmable input signal transition type. A programmable clock divider (prescaler) allows reduction of
the timer input clock frequency. All internal timer interrupt sources are merged in one module interrupt
line and one wake-up line. Each internal interrupt sources can be independently enabled/disabled.
This module is controllable through the OCP peripheral bus.
As two clock domains are managed inside this module, resynchronization is done by special logic
between the OCP clock domain and the Timer clock domain. At reset, synchronization logic allows
utilization of all ratios between the OCP clock and the Timer clock. A drawback of this mode is that
full-resynchronization path is used with access latency performance impact in terms of OCP clock
cycles. In order to improve module access latency, and under restricted conditions on clocks ratios,
write-posted mode can be used by setting the POSTED bit of the System Control Register (TSCR).
Under this mode, write posted mode is enabled, meaning that OCP write command is granted before
write process complete in the timer clock domain. This mode allows software to do concurrent writes on
Dual Mode timer registers and to observe write process completion (synchronization) at the software
level by reading independent write posted status bits in the Write Posted Status Register (TWPS).
17.1.2 Features
The timer consists of the following features:
•
Counter timer with compare and capture modes
•
Auto-reload mode
•
Start-stop mode
•
Programmable divider clock source
•
16-32 bit addressing
•
“On the fly” read/write registers
•
Interrupts generated on overflow, compare and capture
•
Interrupt enable
•
Wake-up enable
•
Write posted mode
•
Dedicated input trigger for capture mode and dedicated output trigger/PWM signal
•
Dedicated output signal for general purpose use PORGPOCFG
•
OCP interface compatible
The Timer resolution and interrupt period are dependent on the selected input clock and clock prescale
value. Example resolutions for common clock values are shown in
.
Table 17-1. Timer Resolution and Maximum Range
Clock
Prescaler
Resolution
Interrupt Period Range
32.768 KHz
1 (min)
31.25 us
31.25 us to ~36h 35m
256 (max)
8 ms
8 ms to ~391d 22h 48m
27 MHz
1 (min)
~37 ns
~37 ns to ~159s
256 (max)
~9.48 us
~19.7 us to ~11h 18m
38.4 MHz
1 (min)
~26 ns
~26 ns to ~112 s
256 (max)
~6.7 us
~13.3 us to ~7h 5m
1634Timers
SPRUGX9 – 15 April 2011
© 2011, Texas Instruments Incorporated
Содержание TMS320C6A816 Series
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