ADUC847 Analog Devices, ADUC847 Datasheet - Page 75

• Manufacturer Part Number: ADUC847
• Description: Precision Analog Microcontroller: 12MIPS 8052 Flash MCU + 10-Ch 24-Bit ADC + 12-Bit DAC
• Manufacturer: Analog Devices

Specifications of ADUC847

• Mcu Core: 8052
• Mcu Speed (mips): 12
• Sram (bytes): 2304Bytes
• Gpio Pins: 34
• Adc # Channels: 10
• Other: PWM

TIMERS/COUNTERS
The ADuC845/ADuC847/ADuC848 have three 16-bit timer/
counters: Timer 0, Timer 1, and Timer 2. The timer/counter
hardware is included on-chip to relieve the processor core of the
overhead inherent in implementing timer/counter functionality
in software. Each timer/counter consists of two 8-bit registers:
THx and TLx (x = 0, 1, or 2). All three can be configured to
operate either as timers or as event counters.
When functioning as a timer, the TLx register is incremented
every machine cycle. Thus, one can think of it as counting
machine cycles. Because a machine cycle on a single-cycle core
consists of one core clock period, the maximum count rate is
the core clock frequency.
TMOD—Timer/Counter 0 and 1 Mode Register
SFR Address:
Power-On Default:
Bit Addressable:
Table 50. TMOD SFR Bit Designation
Bit No.
7
6
5, 4
3
2
1, 0
Name
Gate
C/T
M1, M0
Gate
C/T
M1, M0
89H
00H
No
Description
Timer 1 Gating Control.
Set by software to enable Timer/Counter 1 only while the INT1 pin is high and the TR1 control is set.
Cleared by software to enable Timer 1 whenever the TR1control bit is set.
Timer 1 Timer or Counter Select Bit.
Set by software to select counter operation (input from T1 pin).
Cleared by software to select the timer operation (input from internal system clock).
Timer 1 Mode Select Bits.
M1
0
0
1
1
Timer 0 Gating Control.
Set by software to enable Timer/Counter 0 only while the INT0 pin is high and the TR0 control bit is set.
Cleared by software to enable Timer 0 whenever the TR0 control bit is set.
Timer 0 Timer or Counter Select Bit.
Set by software to the select counter operation (input from T0 pin).
Cleared by software to the select timer operation (input from internal system clock).
Timer 0 Mode Select Bits.
M1
0
0
1
1
M0
0
1
0
1
M0
0
1
0
1
Description
TH1 operates as an 8-bit timer/counter. TL1 serves as 5-bit prescaler.
16-Bit Timer/Counter. TH1 and TL1 are cascaded; there is no prescaler.
8-Bit Autoreload Timer/Counter. TH1 holds a value that is to be reloaded into TL1 each time it
overflows.
Timer/Counter 1 Stopped.
Description
TH0 operates as an 8-bit timer/counter. TL0 serves as a 5-bit prescaler.
16-Bit Timer/Counter. TH0 and TL0 are cascaded; there is no prescaler.
8-Bit Autoreload Timer/Counter. TH0 holds a value that is to be reloaded into TL0 each time it
overflows.
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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When functioning as a counter, the TLx register is incremented
by a 1-to-0 transition at its corresponding external input pin:
T0, T1, or T2. When the samples show a high in one cycle and a
low in the next cycle, the count is incremented. Because it takes
two machine cycles (two core clock periods) to recognize a
1-to-0 transition, the maximum count rate is half 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.
ADuC845/ADuC847/ADuC848