EM78815
8-Bit Microcontroller
7.4 I/O Port
PCRD
P
R
Q
Q
D
CLK
PCWR
C
L
P
R
PORT
Q
Q
D
IOD
CLK
PDWR
PDRD
C
L
0
1
M
U
X
Fig. 27 I/O Port and I/O Control Register Circuit
The I/O registers are bi-directional tri-state I/O ports. The I/O ports can be defined as
"input" or "output" pins by the I/O control registers under program control. The I/O
registers and I/O control registers are both readable and writable. The I/O interface
circuit is shown in Fig. 27.
* The MCU will have a large current consumption when the IO is set to input
and at floating state. Be careful to set unused IO to output or connect them
to VDD or GND when they are set to input status.
Product Specification (V2.4) 08.01.2004
(This specification is subject to change without further notice)
59
ELAN [ ELAN MICROELECTRONICS CORP ]
