AM186ES Advanced Micro Devices, AM186ES Datasheet - Page 126

• Manufacturer Part Number: AM186ES
• Description: microcontrollers provide a low-cost/ high-performance solution for embedded system designers who wish to use the x86 architecture.
• Manufacturer: Advanced Micro Devices

8.3
Table 8-1
8.3.1
8-2
PROGRAMMABLE REGISTERS
The timers are controlled by eleven 16-bit registers (see Table 8-1) that are located in the
peripheral control block.
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.
Each timer also has a maximum-count register that defines the maximum value for the
timer. When the timer reaches the maximum value, it resets to 0 during the same clock
cycle. (The value in the timer-count register never equals the maximum-count register.) In
addition, timers 0 and 1 have a secondary maximum-count register. Using both the primary
and secondary maximum-count registers lets the timer alternate between two maximum
values.
If the timer is programmed to use only the primary maximum-count register, the timer output
pin switches Low for one clock cycle, the clock cycle after the maximum value is reached.
If the timer is programmed to use both of its maximum-count registers, the output pin creates
a waveform by indicating which maximum-count register is currently in control. The duty
cycle and frequency of the waveform depend on the values in the alternating maximum-
count registers.
Timer Operating Frequency
Each timer is serviced on every fourth clock cycle. Therefore, a timer can operate at a
maximum speed of one-quarter of the internal clock frequency. A timer can be clocked
externally at the same maximum frequency of one-fourth of the internal clock frequency.
However, because of internal synchronization and pipelining of the timer circuitry, the timer
output takes up to six clock cycles to respond to the clock or gate input.
The timers are run by the processor internal clock. If power-save mode is in effect, the
timers operate at the reduced power-save clock rate.
Offset from PCB
56h
5Eh
66h
50h
58h
60h
52h
54h
5Ah
5Ch
62h
Register
Mnemonic
T0CON
T1CON
T2CON
T0CNT
T1CNT
T2CNT
T0CMPA
T0CMPB
T1CMPA
T0CMPB
T2CMPA
Timer Control Unit
Register Name
Timer 0 Mode/Control
Timer 1 Mode/Control
Timer 2 Mode/Control
Timer 0 Count
Timer 1 Count
Timer 2 Count
Timer 0 Maxcount Compare A
Timer 0 Maxcount Compare B
Timer 1 Maxcount Compare A
Timer 1 Maxcount Compare B
Timer 2 Maxcount Compare A