Toshiba TX49 TMPR4937, Manual

Page: 388 / 553

Chapter 12 Timer/Counter
12-4
Table 12.3.2 Divide Value and Count (IMBUSCLK = 66 MHz)
Divide
Rate
TMCCDRn.
CCD
Counter Clock
Frequency (Hz)
Resolution (ns)
Max. Set Time
(sec.)
TMCPRAn Value
for 1 sec.
2
4
8
16
32
64
128
256
000
001
010
011
100
101
110
111 33.0 M
16.5 M
8.3 M
4.1 M
2.1 M
1031.3 K
515.6 K
257.8 K
30.30
60.61
121.21
242.42
484.85
969.70
1939.39
3878.79
130.15
260.30
520.60
1041.20
2082.41
4164.82
8329.63
16659.27
33000000
16500000
8250000
4125000
2062500
1031250
515625
257813
12.3.3 Counter
Each channel has an independent 32-bit counter. Set the Timer Count Enable bit (TMTCRn.TCE) and
the 32-bit counter will start counting.
Clear the Timer Count Enable bit to stop the counter. If the Counter Reset Enable bit
(TMTCRn.CRE) is set, then the counter will be cleared also. The Watchdog Timer Disable bit
(TMWTRM2.WDIS) must be set in order to stop and clear this counter when in the Watch Dog Timer
mode.
Also, reading the Timer Read Register (TMTRR) makes it possible to fetch the counter value.
12.3.4 Interval Timer Mode
The Interval Timer mode is used to periodically generate interrupts. Setting the Timer Mode field
(TMTCRn.TMODE) of the Timer Control Register to “00” sets the timer to the Interval Timer mode.
This mode can be used by all timers.
When the count value matches the value of Compare Register A (TMCPRAn), the Interval Timer
TMCPRA Status bit (TMTISRn.TIIS) of the Timer Interrupt Status Register is set. When the Interval
Timer Interrupt Enable bit (TMITMRn.TIIE) of the Interval Timer Mode Register is set, timer interrupts
occur. When a “0” is written to the Interval Timer TMCPRA Status bit (TMTISRn.TIIS), TIIS is cleared
and timer interrupts stop.
If the Timer Zero Clear Enable bit (TMITMRn.TZCE) is set, the counter is cleared to 0 if the count
value matches the Compare Register A (TMCPRAn) value. Count operation stops when the Timer Zero
Clear Enable bit (TMITMRn.TZCE) is cleared.
The level of the TIMER[1:0] output signal stays in the initial state (Low) in this mode. Output is
undefined when changing from the Pulse Generator mode to this mode. Figure 12.3.1 shows an outline
of the count operation and generation of interrupts when in the Interval Timer mode and Figure 12.3.2
shows the operation when using an external input clock.