EM78P5840/5841/5842
8-bit Micro-controller
VII.4 I/O Port
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 data registers and I/O control registers are both readable
and writable. The I/O interface circuit is shown in Fig.9.
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.9_1 The circuit of I/O port and I/O control register
VDD
VDD
VDD
pull
high
PIN
120
ohm
Fig.9_2 The input/output circuit of EM785840 input/output ports
__________________________________________________________________________________________________________________________________________________________________
* This specification is subject to change without notice.
26
2004/11/10 V2.6
ELAN [ ELAN MICROELECTRONICS CORP ]
