King Billion Electronics Co., Ltd
HE84770
駿 億 電 子 股 份 有 限 公 司
HE80000 SERIES
If the dual clock mode is used, the LCD display, Timer1 and Timer Base will derive its clock source from
slow clock while the other blocks will operate with the fast clock.
9.General Purpose I/O
There are three dedicated general purpose I/O port, PRTC, PRTD and PRT10, while PRT14, PRT15 and
PRT17 are multiplexed with LCD segment driver pins. All the I/O Ports are bi-directional and of non-
tri-state output structure. The output has weak sourcing (50 µA) and stronger sinking (1 mA) capability
and each can be configured as push-pull or open-drain output structure individually by mask option.
When the I/O port is used as input, the weakly high sourcing can be used as weakly pull-up. Open drain
can be used if the pull-up is not required and let the external driver to drive the pin. Please note that a
floating pad could cause more power consumption since the noise could interfere with the circuit and
cause the input to toggle. A ‘1’ needs to be written to port first before reading the input data from the I/O
pin. If the PMOS is used as pull-up, care should be taken to avoid the constant power drain by DC path
between pull-up and external circuit.
The input port has built-in Schmidt trigger to prevent it from chattering. Hysteresis level of Schmidt
trigger is 1/3*VDD.
VDD
VDD
DOUT
Q
LATCH
Q'
MO_?PP
PAD
DIN
SCHMIDT Trigger input
As pads of PRT14, PRT15 and PRT17 are shared with LCD segment driver, the function of the pads is
determined by mask options.
August 25, 2003
Page 16 of 30
V2.6E
This specification is subject to change without notice. Please contact sales person for the latest version before use.
KB [ King blillion Electronics Co.,Ltd. ]
