ADUC834 Analog Devices, ADUC834 Datasheet - Page 40

• Manufacturer Part Number: ADUC834
• Description: Precision Analog Microcontroller: 1MIPS 8052 MCU + 62kB Flash + 16/24-Bit ADC + 12-Bit DAC
• Manufacturer: Analog Devices

Specifications of ADUC834

• Mcu Core: 8052
• Mcu Speed (mips): 1
• Sram (bytes): 2304Bytes
• Gpio Pins: 34
• Adc # Channels: 4
• Other: PWM

ADuC834
TIME INTERVAL COUNTER (WAKE-UP/RTC TIMER)
A time interval counter (TIC) is provided on-chip for:
The TIC is capable of timeout intervals ranging from 1/128th
second to 255 hours. Furthermore, this counter is clocked by the
crystal oscillator rather than the PLL and thus has the ability to
remain active in power-down mode and time long power-down
intervals. This has obvious applications for remote battery-powered
sensors where regular widely spaced readings are required.
The TIC counter can easily be used to generate a real-time
clock. The hardware will count in seconds, minutes, and hours;
however, user software will have to count in days, months, and
years. The current time can be written to the timebase SFRs
(HTHSEC, SEC, MIN, and HOUR) while TCEN is low. When
the RTC timer is enabled (TCEN is set), the TCEN bit itself
and the HTHSEC, SEC, MIN, and HOUR Registers are not
reset to 00H after a hardware or watchdog timer reset. This is to
prevent the need to recalibrate the real-time clock after a reset.
However, these registers will be reset to 00H after a power cycle
(independent of TCEN) or after any reset if TCEN is clear.
Six SFRs are associated with the time interval counter, TIMECON
being its control register. Depending on the configuration of the
IT0 and IT1 bits in TIMECON, the selected time counter register
overflow will clock the interval counter. When this counter is
equal to the time interval value loaded in the INTVAL SFR, the
TII bit (TIMECON.2) is set and generates an interrupt if enabled.
(See IEIP2 SFR description under Interrupt System in this data
Bit
7
6
5
4
3
2
1
0
• periodically waking the part up from power-down
• implementing a Real-Time Clock
• counting longer intervals than the standard 8051 compatible
timers are capable of
Name
–––
–––
ITS1
ITS0
STI
TII
TIEN
TCEN
Description
Reserved for Future Use
Reserved for Future Use. For future product code compatibility, this bit should be written as a ‘1.’
Interval Timebase Selection Bits
Written by user to determine the interval counter update rate.
ITS1
0
0
1
1
Single Time Interval Bit.
Set by user to generate a single interval timeout. If set, a timeout will clear the TIEN bit.
Cleared by user to allow the interval counter to be automatically reloaded and start counting again at
each interval timeout.
TIC Interrupt Bit.
Set when the 8-bit Interval Counter matches the value in the INTVAL SFR.
Cleared by user software.
Time Interval Enable Bit.
Set by user to enable the 8-bit time interval counter.
Cleared by user to disable and clear the contents of the 8-bit interval counter. To ensure that the
8-bit interval counter is cleared TIEN must be held low for at least 30.5 s (32 kHz).
Time Clock Enable Bit.
Set by user to enable the time clock to the time interval counters.
Cleared by user to disable the 32 kHz clock to the TIC and clear the 8-bit prescaler and the HTHSEC,
SEC, MIN and HOURS SFRs. To ensure that these registers are cleared, TCEN must be held low for at
least 30.5 s (32 kHz). The time registers (HTHSEC, SEC, MIN, and HOUR) can only be written
while TCEN is low.
Table XVIII. TIMECON SFR Bit Designations
ITS0
0
1
0
1
Interval Timebase
1/128 Second
Seconds
Minutes
Hours
–40–
sheet.) If the ADuC834 is in power-down mode, again with TIC
interrupt enabled, the TII bit will wake up the device and resume
code execution by vectoring directly to the TIC interrupt service
vector address at 0053H. The TIC-related SFRs are described
below with a block diagram of the TIC shown in Figure 33.
TIME INTERVAL COUNTER INTERRUPT
TCEN
32.768kHz EXTERNAL CRYSTAL
INTERVAL TIMEOUT
Figure 33. TIC, Simplified Block Diagram
HUNDREDTHS COUNTER
SECOND COUNTER
MINUTE COUNTER
HOUR COUNTER
PRESCALER
HOUR
8-BIT
HTHSEC
SEC
MIN
INTERVAL COUNTER
INTVAL SFR
EQUAL?
8-BIT
SELECTION
TIMEBASE
INTERVAL
ITS0, 1
MUX
REV. A
TIEN