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46R01A3

Small Package A/D Type 8-Bit OTP MCU

Holtek Semiconductor 

HT46R01A

In addition, on entering an interrupt sequence or execut-

ing a subroutine call, the status register will not be

pushed onto the stack automatically. If the contents of

the status registers are important and if the interrupt rou-

tine can change the status register, precautions must be

taken to correctly save it.

Interrupt Control Registers - INTC0

The 8-bit register, known as INTC0, control the opera-

tion of both external, and internal timer and A/D inter-

rupts. By setting various bits within this register using

standard bit manipulation instructions, the enable/dis-

able function of each interrupt can be independently

controlled. A master interrupt bit within this register, the

EMI bit, acts like a global enable/disable and is used to

set all of the interrupt enable bits on or off. This bit is

cleared when an interrupt routine is entered to disable

further interrupt and is set by executing the ²RETI² in-

struction.

Timer/Event Counter Registers

Depending upon which device is selected, all devices

contain one or two integrated 8-bit Timer/Event Coun-

ters. For the device, which have a single 8-bit Timer/

Event Counter, an associated register known as TMR0

is the location where the timer¢s 8-bit value is located.

An associated control register, known as TMR0C, con-

tains the setup information for this timer.

Input/Output Ports and Control Registers

Within the area of Special Function Registers, the port

PA data I/O register and its associated control register

PAC play a prominent role. These registers are mapped

to specific addresses within the Data Memory as shown

in the Data Memory table. The PA data I/O register, is

used to transfer the appropriate output or input data on

the PA port. The PAC control register specifies which

pins of PA are set as inputs and which are set as out-

puts. To setup a pin as an input, the corresponding bit of

the control register must be set high, for an output it

must be set low. During program initialisation, it is impor-

tant to first setup the control registers to specify which

pins are outputs and which are inputs before reading

data from or writing data to the I/O ports. One flexible

feature of these registers is the ability to directly pro-

gram single bits using the ²SET [m].i² and ²CLR [m].i²

instructions. The ability to change I/O pins from output to

input and vice versa by manipulating specific bits of the

I/O control registers during normal program operation is

a useful feature of these devices.

Pulse Width Modulation Register - PWM

Each device contains a Pulse Width Modulator which

has a corresponding control register, known as PWM.

The 8-bit contents of this register defines the duty cycle

value for the modulation cycle of the Pulse Width Modu-

lator.

A/D Converter Register - ADR, ADCR, ACSR

The device contains a 4-channel 8-bit A/D converter,

which has a single data register, known as ADR. This is

the register where the digital value is placed after the

completion of an analog to digital conversion cycle. The

channel selection and configuration of the A/D converter

is setup via the control register ADCR while the A/D

clock frequency is defined by the clock source register,

ACSR.

System Control Register - CTRL0

This register is used to provide control over certain inter-

nal functions including certain system clock options, the

PFD clock source and on/off control, the PWM mode

and on/off control and an RTC Oscillator quick start up

function.

System Control Register - CTRL1

This register is used to provide control over certain inter-

nal functions including the External Interrupt edge trig-

ger type and the Watchdog Timer control function.

Wake-up Function Register - PAWK

When the microcontroller enters the Power Down Mode,

various methods exist to wake the device up and con-

tinue with normal operation. One method is to allow a

low going edge on the I/O pins to have a wake-up func-

tion. This register is used to select which I/O pins are

used to have this wake-up function.

Pull-high Register - PAPU

The I/O pins, if configured as inputs, can have internal

pull-high resistors connected, which eliminates the need

for external pull-high resistors. This register selects which

I/O pins are connected to internal pull-high resistors.

Rev. 1.10

13

August 13, 2008

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