em78p210n ELAN Microelectronics Corp, em78p210n Datasheet - Page 27

• Manufacturer Part Number: em78p210n
• Description: 8-bit Microcontroller With Otp Rom
• Manufacturer: ELAN Microelectronics Corp

Product Specification (V1.2) 04.22.2008
(This specification is subject to change without further notice)
1
VDD=5V, WDT Time-out period = 15.2ms ± 30%.
VDD=3V, WDT Time-out period = 18ms ± 30%.
6.3 TCC/WDT and Prescaler
There are two 8-bit counters available as prescalers for the TCC and WDT. The
PST2~PST0 bits of the CONT register are used to determine the ratio of the TCC
prescaler, and the PSW2~PSW0 bits of the Bank 1-RE register are used to determine
the WDT prescaler. The prescaler counter is cleared by the instructions each time
such instructions are written into TCC. The WDT and prescaler are cleared by the
“WDTC” and “SLEP” instructions. Figure 6-2 depicts the block diagram of TCC/WDT.
TCC (Bank 3-R5) is an 8-bit timer/counter. The TCC clock source can be internal clock
(Fosc) or external signal input (edge selectable from the TCC pin). If the TCC signal
source is from an external clock input, TCC will be incremented by 1 at every falling
edge or rising edge of the TCC pin. The TCC pin input time length (kept at High or Low
level) must be greater than 1CLK. 1 CLK is always Fosc/2. Refer to Figure 6-2.
The watchdog timer is a free running on-chip RC oscillator. The WDT will keep on
running even when the oscillator driver has been turned off (i.e., in sleep mode).
During normal operation or sleep mode, a WDT time-out (if enabled) will cause the
device to reset. The WDT can be enabled or disabled at any time during normal mode
through software programming. Refer to WDTE bit of Bank 1-RE register (Section
6.2.10 Bank 1-RE (WDT Control Register). With no prescaler, the WDT time-out
duration is approximately 18ms.
WDTE (Bank 1-RE)
TE (CONT)
TCC Pin
WDT
CLK (Fosc)
The internal TCC will stop running when in sleep mode.
WDT Time out
Figure 6-3 TCC and WDT Block Diagram
8-bit Counter
8 to 1 MUX
1
0
TS (CONT)
MUX
1
NOTE
8-bit Counter
8 to 1 MUX
Prescaler
Prescaler
(Bank 1-RE)
PST2~0
PSW2~0
(CONT)
8-Bit Microcontroller with OTP ROM
EM78P210N
TCC overflow
TCC (R1)
Data Bus
Interrupt
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