EVAL-ADUC831QSZ Datasheet, PDF (50/76 Pages) Analog Devices – MicroConverter®, 12-Bit ADCs and DACs with Embedded 62 kBytes Flash MCU

ADuC831
Timers/Counters
The ADuC831 has three 16-bit Timer/Counters: Timer 0,
Timer 1, and Timer 2. The Timer/Counter hardware has been
included on-chip to relieve the processor core of the overhead
inherent in implementing Timer/Counter functionality in soft-
ware. Each Timer/Counter consists of two 8-bit registers THx
and TLx (x = 0, 1, and 2). All three can be configured to oper-
ate either as timers or event counters.
In “Timer” function, the TLx register is incremented every
machine cycle. Thus, one can think of it as counting machine
cycles. Since a machine cycle consists of 12 core clock periods,
the maximum count rate is 1/12 of the core clock frequency.
In “Counter” function, the TLx register is incremented by a 1-to-0
transition at its corresponding external input pin, T0, T1, or T2.
In this function, the external input is sampled during S5P2 of
every machine cycle. When the samples show a high in one
cycle and a low in the next cycle, the count is incremented. The
new count value appears in the register during S3P1 of the cycle
following the one in which the transition was detected. Since it
takes two machine cycles (24 core clock periods) to recognize a
1-to-0 transition, the maximum count rate is 1/24 of the core
clock frequency. There are no restrictions on the duty cycle of the
external input signal, but to ensure that a given level is sampled
at least once before it changes, it must be held for a minimum of
one full machine cycle.
User configuration and control of all Timer operating modes is achieved via three SFRs:
TMOD, TCON
Control and configuration for Timers 0 and 1.
T2CON
Control and configuration for Timer 2.
TMOD
SFR Address
Power-On Default Value
Bit Addressable
Timer/Counter 0 and 1 Mode Register
89H
00H
No
Table XIX. TMOD SFR Bit Designations
Bit
Name
Description
7
Gate
Timer 1 Gating Control.
Set by software to enable timer/counter 1 only while INT1 pin is high and TR1 control bit is set.
Cleared by software to enable Timer 1 whenever TR1 control bit is set.
6
C/T
Timer 1 Timer or Counter Select Bit.
Set by software to select counter operation (input from T1 pin).
Cleared by software to select timer operation (input from internal system clock).
5
M1
Timer 1 Mode Select Bit 1 (Used with M0 Bit).
4
M0
Timer 1 Mode Select Bit 0.
M1
M0
0
0
TH1 operates as an 8-bit timer/counter. TL1 serves as 5-bit prescaler.
0
1
16-Bit Timer/Counter. TH1 and TL1 are cascaded; there is no prescaler.
1
0
8-Bit Auto-Reload Timer/Counter. TH1 holds a value which is to be
reloaded into TL1 each time it overflows.
1
1
Timer/Counter 1 Stopped.
3
Gate
Timer 0 Gating Control.
Set by software to enable timer/counter 0 only while INT0 pin is high and TR0 control bit is set.
Cleared by software to enable Timer 0 whenever TR0 control bit is set.
2
C/T
Timer 0 Timer or Counter Select Bit.
Set by software to select counter operation (input from T0 pin).
Cleared by software to select timer operation (input from internal system clock).
1
M1
Timer 0 Mode Select Bit 1.
0
M0
Timer 0 Mode Select Bit 0.
M1
M0
0
0
TH0 operates as an 8-bit timer/counter. TL0 serves as 5-bit prescaler.
0
1
16-Bit Timer/Counter. TH0 and TL0 are cascaded; there is no prescaler.
1
0
8-Bit Auto-Reload Timer/Counter. TH0 holds a value which is to
be reloaded into TL0 each time it overflows.
1
1
TL0 is an 8-bit timer/counter controlled by the standard timer 0 control bits.
TH0 is an 8-bit timer only, controlled by Timer 1 control bits.
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