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EM78P159NKM

8-Bit Microcontroller with OTP ROM

ELAN Microelectronics 

EM78P159N

8-Bit Microcontrollerwith OTP ROM

4.4 I/O Ports

The I/O registers, both Port 5 and Port 6, are bi-directional tri-state I/O ports. Port 6 can

be pulled high internally by software. In addition, Port 6 can also features an

open-drain output through software and an Input status change interrupt (or wake-up)

function. P50 ~ P53 and P60 ~ P63 pins can be pulled down by software. Each I/O pin

can be defined as "input" or "output" pin by the I/O control register (IOC5 ~ IOC6).

P50~P51 are the R-option pins enabled by setting the ROC bit in the IOCE register to

“1.” When the R-option function is used, it is recommended that P50 ~ P51 are used as

output pins. When R-option is in enable state, P50 ~ P51 must be programmed as

input pins. Under R-option mode, the current/power consumption by Rex should be

taken into the consideration to promote energy conservation.

The I/O registers and I/O control registers are both readable and writable. The I/O

interface circuits for Port 5 and Port 6 are shown in the following figures (Figures 4-3,

4-4a, 4-4b, & 4-5).

PCRD

Q

P

R

D

_

Q

CLK

C

L

PCWR

PORT

0

M

U

1

X

Q

P

R

D

_

CLK

C

Q

L

PDWR

PDRD

IOD

Figure 4-3 I/O Port and I/O Control Register for Port 5 Circuit

NOTE

Pull-down is not shown in the figure.

16 •

Product Specification (V1.0) 03.10.2006

(This specification is subject to change without further notice)

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