aduc831bcp-reel Analog Devices, Inc., aduc831bcp-reel Datasheet - Page 52

• Manufacturer Part Number: aduc831bcp-reel
• Description: Microconverter, 12-bit Adcs And Dacs With Embedded 62 Kbytes Flash Mcu
• Manufacturer: Analog Devices, Inc.

ADuC831
TIMER/COUNTER 0 AND 1 OPERATING MODES
The following paragraphs describe the operating modes for
Timer/Counters 0 and 1. Unless otherwise noted, it should be
assumed that these modes of operation are the same for Timer 0
as for Timer 1.
Mode 0 (13-Bit Timer/Counter)
Mode 0 configures an 8-bit Timer/Counter with a divide-by-32
prescaler. Figure 45 shows mode 0 operation.
In this mode, the timer register is configured as a 13-bit register.
As the count rolls over from all 1s to all 0s, it sets the timer over-
flow flag TF0. The overflow flag, TF0, can then be used to request
an interrupt. The counted input is enabled to the timer when
TR0 = 1 and either Gate = 0 or INT0 = 1. Setting Gate = 1
allows the timer to be controlled by external input INT0, to
facilitate pulsewidth measurements. TR0 is a control bit in the
special function register TCON; Gate is in TMOD. The 13-bit
register consists of all eight bits of TH0 and the lower five bits of
TL0. The upper three bits of TL0 are indeterminate and should
be ignored. Setting the run flag (TR0) does not clear the registers.
Mode 1 (16-Bit Timer/Counter)
Mode 1 is the same as Mode 0, except that the timer register is
running with all 16 bits. Mode 1 is shown in Figure 46.
P3.4/T0
P3.2/INT0
P3.4/T0
P3.2/INT0
CORE
CORE
CLK
CLK
GATE
GATE
Figure 45. Timer/Counter 0, Mode 0
Figure 46. Timer/Counter 0, Mode 1
12
12
TR0
TR0
C/ T = 0
C/ T = 1
C/ T = 0
C/ T = 1
CONTROL
CONTROL
(5 BITS)
(8 BITS)
TL0
TL0
(8 BITS)
(8 BITS)
TH0
TH0
TF0
TF0
INTERRUPT
INTERRUPT
–52–
Mode 2 (8-Bit Timer/Counter with Autoreload)
Mode 2 configures the timer register as an 8-bit counter (TL0)
with automatic reload, as shown in Figure 47. Overflow from
TL0 not only sets TF0, but also reloads TL0 with the contents
of TH0, which is preset by software. The reload leaves TH0
unchanged.
Mode 3 (Two 8-Bit Timer/Counters)
Mode 3 has different effects on Timer 0 and Timer 1. Timer 1 in
Mode 3 simply holds its count. The effect is the same as setting
TR1 = 0. Timer 0 in Mode 3 establishes TL0 and TH0 as two
separate counters. This configuration is shown in Figure 50.
TL0 uses the Timer 0 control bits: C/T, Gate, TR0, INT0, and
TF0. TH0 is locked into a timer function (counting machine
cycles) and takes over the use of TR1 and TF1 from Timer 1.
Thus, TH0 now controls the Timer 1 interrupt. Mode 3 is
provided for applications requiring an extra 8-bit timer or counter.
When Timer 0 is in Mode 3, Timer 1 can be turned on and off
by switching it out of, and into, its own Mode 3, or can still be
used by the serial interface as a baud rate generator. In fact, it can
be used in any application not requiring an interrupt from
Timer 1 itself.
P3.4/T0
P3.2/INT0
P3.2/INT0
P3.4/T0
CORE
CLK
CLK/12
GATE
CORE
CLK
CORE
GATE
TR1
Figure 47. Timer/Counter 0, Mode 2
Figure 48. Timer/Counter 0, Mode 3
12
12
TR0
TR0
C/ T = 0
C/ T = 1
C/ T = 0
C/ T = 1
CORE
CLK/12
CONTROL
CONTROL
RELOAD
(8 BITS)
(8 BITS)
(8 BITS)
(8 BITS)
TH0
TL0
TH0
TL0
TF0
TF1
TF0
INTERRUPT
REV. 0
INTERRUPT
INTERRUPT