IBM EM78P259N/260N manual

EM78P259N/260N

8-Bit Microprocessor with OTP ROM

„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 is cleared

„The IOCB0 register bits are set to all "1"

„The IOCC0 register bits are set to all "1"

„The IOCD0 register bits are set to all "1"

„Bits 7, 5, and 4 of IOCE0 register is cleared

„Bit 5 and 4 of RE register is cleared

„RF and IOCF0 registers are cleared

Executing the “SLEP” instruction will assert the sleep (power down) mode. While entering into sleep mode, the Oscillator, TCC, TCCA, TCCB, and TCCC are stopped. The WDT (if enabled) is cleared but keeps on running.

During AD conversion, when “SLEP” instruction I set; the Oscillator, TCC, TCCA, TCCB, and TCCC keep on running. The WDT (if enabled) is cleared but keeps on running.

The controller can be awakened by:

Case 1 External reset input on /RESET pin

Case 2 WDT time-out (if enabled)

Case 3 Port 5 input status changes (if ICWE is enabled)

Case 4 Comparator output status changes (if CMPWE is enabled)

Case 5 AD conversion completed (if ADWE enable)

The first two cases (1 & 2) will cause the EM78P260N to reset. The T and P flags of R3 can be used to determine the source of the reset (wake-up). Cases 3, 4, & 5 are considered the continuation of program execution and the global interrupt ("ENI" or "DISI" being executed) decides whether or not the controller branches to the interrupt vector following wake-up. If ENI is executed before SLEP, the instruction will begin to execute from address 0x06 (Case 3), 0x0F (Case 4), and 0x0C (Case 5) after wake-up. If DISI is executed before SLEP, the execution will restart from the instruction next to SLEP after wake-up.

Only one of Cases 2 to 5 can be enabled before entering into sleep mode. That is:

Case [a] If WDT is enabled before SLEP, all of the RE bit is disabled. Hence, the EM78P259N/260N can be awakened only with Case 1 or Case 2. Refer to the section on Interrupt (Section 6.6 below) for further details.

Case [b] If Port 5 Input Status Change is used to wake -up EM78P259N/260N and the ICWE bit of RE register is enabled before SLEP, WDT must be disabled. Hence, the EM78P259N/260N can be awakened only with Case 3. Wake-up time is dependent on oscillator mode. In RC mode, Wake-up time is 32 clocks (for stable oscillators). In High Crystal mode, Wake-up time is 2ms and 32clocks (for stable oscillators); and in low Crystal mode, Wake-up time is 500ms.

32 •	Product Specification (V1.2) 05.18.2007
	(This specification is subject to change without further notice)