em78p862a ELAN Microelectronics Corp, em78p862a Datasheet - Page 26

• Manufacturer Part Number: em78p862a
• Description: 8-bit Risc Type Microprocessor
• Manufacturer: ELAN Microelectronics Corp

EM78862B
8-Bit RISC Type Microprocessor
20 of 35
08.02.2004 (V1.0)
6.4
The I/O registers, (Port 5, Port 6, Port 7, Port 8, and Port 9), are bi-directional tri-state I/O ports.
Port 7 can be pulled-high internally by software. Furthermore, P7.6 and P7.7 has its
open-drain output also defined through software. Port 9 features an input status changed
wake-up function. Each I/O pin can be defined as "input" or "output" pin by the I/O control
register (IOC5 ~ IOC9). The I/O registers and I/O control registers are both readable and
writable. The I/O interface circuits are shown in Fig. 10 below.
6.5
RESET will occur during any of the following conditions:
Once a RESET occurs, the following functions are performed:
Power on reset
WDT timeout (if WDT is enabled during SLEEP, GREEN, or NORMAL mode)
Port 9 wake-up (if WUP9H or WUP9L is enabled during SLEEP mode)
RESET pin pull low
The oscillator will continue running
The Program Counter (R2) is set to all "0"
All I/O port pins are configured to input mode (high-impedance state)
The TCC/Watchdog timer and pre-scaler are cleared
The Watchdog timer is disabled
When power is switched on, the upper 3 bits of R3 and the upper 2 bits of R4 are cleared
The bits of the CONT register are set to all "1"
NOTE: Open-drain is not
I/O Ports
RESET and Wake-up
Fig. 10 Port 5, Port 6, Port 7, & Port 8 I/O Port and I/O Control Register Circuit
shown in the figure.
This specification is subject to change without further notice.