em78p164n ELAN Microelectronics Corp, em78p164n Datasheet - Page 25

• Manufacturer Part Number: em78p164n
• Description: 8-bit Microcontroller With Otp Rom
• Manufacturer: ELAN Microelectronics Corp

Product Specification (V1.4) 05.28.2010
(This specification is subject to change without further notice)
5.3 TCC/WDT and Prescaler
There are two 8-bit counters available as prescalers for the TCC and WDT respectively.
The PST0 ~ PST2 bits of the CONT register are used to determine the ratio of the TCC
prescaler, and the PSW0 ~ PSW2 bits of the IOCE0 register are used to determine the
WDT prescaler. The prescaler counter is cleared by the instructions each time such
instructions are written into the TCC. The WDT and prescaler will be cleared by the
“WDTC” and “SLEP” instructions. Figure 5-4 depicts the block diagram of TCC/WDT.
TCC (R1) is an 8-bit timer/counter. The TCC clock source can be an internal clock or
external signal input (edge selectable from the TCC pin). If the TCC signal source is
from an internal clock, TCC will increase by 1 at every 1/Fc clock (without prescaler). If
TCC signal source is from the 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.
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 any time during normal mode
through software programming. Refer to WDTE bit of the IOCE0 register. Without
prescaler, the WDT time-out duration is approximately 18ms.
1
VDD=5V, Setup time period = 16.5ms ± 30%.
TE (CONT)
VDD=3V, Setup time period = 18ms ± 30%.
(IOCE0)
TCC Pin
WDTE
WDT
CLK (Fosc/2 or Fosc/4)
WDT Time out
8-Bit Counter
8 to 1 MUX
0
1
TS (CONT)
Figure 5-4 TCC and WDT Block Diagram
MUX
8-Bit Counter (IOCC1)
8 to 1 MUX
Prescaler
Prescaler
PSR2~0
(CONT)
PSW2~0
(IOCE0)
8-Bit Microcontroller with OTP ROM
1
2 cycles
SYNC
EM78P164N
TCC overflow
TCC (R1)
Data Bus
interrupt
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