HT46R0664 datasheet(44/92 Pages) HOLTEK

44 / 92 page

Rev. 1.00

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Rev. 1.00

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HT46R0664

Enhanced A/D+LCD Type 8-Bit OTP MCU

R ead Da ta R egi st er

CK S

Co nt ro l Bi t

Da ta B us

Wr it e C ont ro l Re gi st er

Ch ip R es et

Re ad C on tr ol R eg is te r

Wr it e Da ta R egi st er

Da ta B it

PA7

PA WK 7

S yst em W ak e- up( PA7 )

PA7 NMOS Input/Output Port

Programming Considerations

Within the user program, one of the things first to consider is port initialisation. After a reset, all

of the I/O data and port control registers will be set to high. This means that all I/O pins will be

defaulted to an input state, the level of which depends on the other connected circuitry and whether

pull-high selections have been chosen. If the port control registers are then programmed to setup

some pins as outputs, these output pins will have an initial high output value unless the associated

port data registers are first programmed. Selecting which pins are inputs and which are outputs can

be achieved byte-wide by loading the correct values into the appropriate port control register or

by programming individual bits in the port control register using the “SET [m].i” and “CLR [m].i”

instructions. Note that when using these bit control instructions, a read-modify-write operation takes

place. The microcontroller must first read in the data on the entire port, modify it to the required new

bit values and then rewrite this data back to the output ports.

System Clock

Port Data

Read from Port

Write to Port

Read Modify Write Timing

Port A has the additional capability of providing wake-up functions. When the device is in the

SLEEP or IDLE Mode, various methods are available to wake the device up. One of these is a high

to low transition of any of the Port A pins. Single or multiple pins on Port A can be setup to have this

function.

HT46R0664 датащи(PDF) 44 Page - Holtek Semiconductor Inc