AMD Am186TMER ユーザーズマニュアル
Timer Control Unit
9-1
CHAPTER
9
TIMER CONTROL UNIT
9.1
OVERVIEW
There are three 16-bit programmable timers in the Am186ER and Am188ER
microcontrollers. Timers 0 and 1 are highly versatile and are each connected to two external
pins (each one has an input and an output). These two timers can be used to count or time
external events, or they can be used to generate nonrepetitive or variable-duty-cycle
waveforms. Timer 1 can also be configured as a watchdog timer.
microcontrollers. Timers 0 and 1 are highly versatile and are each connected to two external
pins (each one has an input and an output). These two timers can be used to count or time
external events, or they can be used to generate nonrepetitive or variable-duty-cycle
waveforms. Timer 1 can also be configured as a watchdog timer.
The watchdog timer provides a mechanism for detecting software crashes or hangs. The
TMROUT1 output is internally connected to the watchdog timer interrupt. Software
developers must first program the TIMER1 Mode/Control, Count, and Max Count registers,
and then program the Watchdog Timer Interrupt Control register (see Figure 8-8 on page
8-19). The TIMER1 Count register must be reloaded at intervals less than the TIMER1 max
count to assure the watchdog interrupt is not taken. If the code crashes or hangs, the
TIMER1 countdown can cause a watchdog interrupt.
TMROUT1 output is internally connected to the watchdog timer interrupt. Software
developers must first program the TIMER1 Mode/Control, Count, and Max Count registers,
and then program the Watchdog Timer Interrupt Control register (see Figure 8-8 on page
8-19). The TIMER1 Count register must be reloaded at intervals less than the TIMER1 max
count to assure the watchdog interrupt is not taken. If the code crashes or hangs, the
TIMER1 countdown can cause a watchdog interrupt.
Timer 2 is not connected to any external pins. It can be used for real-time coding and time-
delay applications. It can also be used as a prescale to timer 0 and timer 1 or as a DMA
request source.
delay applications. It can also be used as a prescale to timer 0 and timer 1 or as a DMA
request source.
9.2
PROGRAMMABLE REGISTERS
The timers are controlled by eleven 16-bit registers (see Table 9-1) that are located in the
peripheral control block.
peripheral control block.
Table 9-1
Timer Control Unit Register Summary
The timer-count registers contain the current value of a timer. The timer-count registers
can be read or written at any time, regardless of whether the corresponding timer is running.
The microcontroller increments the value of a timer-count register each time a timer event
occurs.
can be read or written at any time, regardless of whether the corresponding timer is running.
The microcontroller increments the value of a timer-count register each time a timer event
occurs.
Offset from
PCB
PCB
Register
Mnemonic
Mnemonic
Register Name
56h
T0CON
Timer 0 Mode/Control
5Eh
T1CON
Timer 1 Mode/Control
66h
T2CON
Timer 2 Mode/Control
50h
T0CNT
Timer 0 Count
58h
T1CNT
Timer 1 Count
60h
T2CNT
Timer 2 Count
52h
T0CMPA
Timer 0 Maxcount Compare A
54h
T0CMPB
Timer 0 Maxcount Compare B
5Ah
T1CMPA
Timer 1 Maxcount Compare A
5Ch
T0CMPB
Timer 1 Maxcount Compare B
62h
T2CMPA
Timer 2 Maxcount Compare A