em78p257 ELAN Microelectronics Corp, em78p257 Datasheet - Page 32

• Manufacturer Part Number: em78p257
• Description: 8-bit Microcontroller
• Manufacturer: ELAN Microelectronics Corp

4.5 RESET and Wake-up
This specification is subject to change without prior notice.
1. RESET
Table 5 Usage of Port 5 Input Status Changed Wake-up/Interrupt Function
A RESET is initiated by one of the following events-
The device is kept in a RESET condition for a period of approximately 18ms
period) after the reset is detected. The initial address is 000h.Once the RESET occurs, the following events are
performed.
1
2
NOTE:
NOTE:
(I) Wake-up from Port 5 Input Status Change
(1) Power on reset;
(2) /RESET pin input "low", or
(3) Watch dog timer time-out (if enabled).
(b) After Wake-up
• The oscillator is running, or will be started.
• The Program Counter (R2) is set to all "0".
• All I/O port pins are configured as input mode (high-impedance state).
• The Watchdog timer and prescaler are cleared.
• When power is switched on, the upper 3 bits of R3 are cleared.
• The bits of the CONT register are set to all "1" except for the Bit 6 (INT flag).
• The bits of the IOCB0 register are set to all "1".
• The IOCC0 register is cleared.
• The bits of the IOCD0 register are set to all "1".
(a) Before SLEEP
1. Disable WDT
2. Read I/O Port 5 (MOV R5,R5)
3. Execute "ENI" or "DISI"
4. Enable interrupt (Set IOCF0.1)
5. Execute "SLEP" instruction
1. IF "ENI"
2. IF "DISI"
VDD=5V, Setup time period = 15.4ms ± 30%.
VDD=3V, Setup time period = 17.6ms ± 30%.
VDD=5V, Setup time period = 1.07ms ± 30%.
VDD=3V, Setup time period = 1.22ms ± 30%.
Interrupt vector (3FEH)
Next instruction
Usage of Port 5 input status changed Wake-up/Interrupt
32
(II) Port 5 Input Status Change Interrupt
1. Read I/O Port 5 (MOV R5,R5)
2. Execute "ENI"
3. Enable interrupt (Set IOCF0.1)
4. IF Port 5 change (interrupt)
Interrupt vector (3FEH)
1
or 1ms
2
(one oscillator start-up timer
EM78P257
07.27.2004 (V1.4)
OTP ROM