em78p210n ELAN Microelectronics Corp, em78p210n Datasheet - Page 28

• Manufacturer Part Number: em78p210n
• Description: 8-bit Microcontroller With Otp Rom
• Manufacturer: ELAN Microelectronics Corp

EM78P210N
8-Bit Microcontroller with OTP ROM
22 •
6.4 I/O Ports
The I/O registers (Port 5, Port 6, Port 7, and Port 8) are bidirectional tri-state I/O ports.
The Pull-high, Pull-down, and Open-drain functions can be set internally by Bank 1-RB,
Bank 1-RC, and Bank 1-RD respectively. The High drive and High Sink functions can
be set internally by Bank 2-R5, Bank 2-R6, and Bank 2-R7 respectively. Port 6 features
an input status change interrupt (or wake-up) function. Most I/O pin can be defined as
"input" or "output" pin by the I/O control registers. The I/O registers and I/O control
registers are both readable and writable. However, the initial states of these I/O ports
(Port 5, Port 6, Port 7 and Port 8) are unknown input (high impedance). Then, if the I/O
pin is pulled to a level at external circuit, the pin must induce a voltage. Hence, user
must take into consideration whether the induced voltage causes a wrong action in the
system. The I/O interface circuits for Port 5, Port 6, Port 7, and Port 8 are illustrated in
Figures 6-4, 6-5, & 6-6 respectively. Port 6 with Input Change Interrupt/Wake-up is
shown in Figure 6-7.
Figure 6-4 I/O Port and I/O Control Register Circuit for Port 5 , Port 7 and Port 8
Note: Pull-high and Open-drain are not shown in the figure.
PORT
0
1
M
U
X
(This specification is subject to change without further notice)
PCRD
Q
Q
Q
Q
_
_
P
R
C
L
P
R
C
L
CLK
CLK
D
D
Product Specification (V1.2) 04.22.2008
PDRD
PCWR
PDWR
IOD