HT37B70 datasheet(21/80 Pages) HOLTEK

21 / 80 page

HT37B90/HT37B70/HT37B50/HT37B30

Rev.1.00

June22,2017

SPI Registers - SBCR, SBDR

The device contain an internal SPI function which is

controlled via these two registers. The SBCR is the sta-

tus and control register for the SPI function. The actual

data that is to be transmitted or that is received on the

serialinterfaceisstoredinthe SBDR register.

UART Registers - RS232C, TXD, RXD, BRGR

The device contain an internal UART function which is

controlled via these four registers. The RS232C is the

status and control register for the UART .The actual data

that is to be transmitted or that is received on the serial

interface is stored in the TXD/RXD register. The BRGR

31.25kHzaccordingto fOSC.

Input/OutputPorts

Holtek microcontrollers offer considerable flexibility on

their I/O ports. With the input or output designation of ev-

ery pin fully under user program control, pull-high op-

tions for all ports and wake-up options on certain pins,

the user is provided with an I/O structure to meet the

needs of a wide range of application possibilities. De-

pending upon which device or package is chosen, the

microcontroller range provides from 32 to 40

bidirectional input/output lines labeled with port names

PA, PB, PC, PD and PE. These I/O ports are mapped to

the RAM Data Memory with specific addresses as

shown in the Special Purpose Data Memory table. All of

these I/O ports can be used for input and output opera-

tions. For input operation, these ports are non-latching,

which means the inputs must be ready at the T2 rising

edge of instruction

²MOV A,[m]², where m denotes the

portaddress.

For output operation, all the data is latched and remains

unchangeduntiltheoutputlatchisrewritten.

Pull-highResistors

Many product applications require pull-high resistors for

their switch inputs usually requiring the use of an exter-

nal resistor. To eliminate the need for these external re-

sistors, I/O pins PA~PE, when configured as an input

have the capability of being connected to an internal

pull-high resistor. These pull-high resistors are

selectable via PA~PE option respectively, located in the

configuration. The pull-high resistors are implemented

usingweak PMOS transistors.

PortAWake-up

If the HALT instruction is executed, the device will enter

the Power Down Mode, where the system clock will stop

resulting in power being conserved, a feature that is im-

portantforbatteryandotherlow-powerapplications.

Various methods exist to wake-up the microcontroller,

one of which is to change the logic condition on one of

the PA0~PA7 pins from high to low. After a HALT instruc-

tion forces the microcontroller into entering the Power

Down Mode, the processor will remain idle or in a

low-power state until the logic condition of the selected

wake-up pin on Port A changes from high to low. This

function is especially suitable for applications that can

be woken up via external switches. Note that pins PA0 to

PA7 can be selected individually to have this wake-up

feature using an PA wake up option, located in the con-

figuration.

I/OPortControlRegisters

Each I/O port have their own control register, known as

PAC, PBC, PCC, PDC and PEC, which control the in-

put/output configuration. With this control register, each

PA~PE I/O pin with or without pull-high resistors can be

reconfigured by pull-hi option control. Pins PA~PE ports

are directly mapped to a bit in its associated port control

sponding bit of the control register must be written as a

²1². This will then allow the logic state of the input pin to

be directly read by instructions. When the correspond-

ing bit of the control register is written as a

²0², the I/O

pin will be setup as a CMOS output. If the pin is currently

setup as an output, instructions can still be used to read

theoutputregister.

However, it should be noted that the program will in fact

only read the status of the output data latch and not the

actuallogicstatusoftheoutputpin.

· Pin-sharedFunctions

The flexibility of the microcontroller range is greatly

enhanced by the use of pins that have more than one

function. Limited numbers of pins can force serious

design constraints on designers but by supplying pins

with multi-functions, many of these difficulties can be

overcome. For some pins, the chosen function of the

multi-function I/O pins is set by configuration options

while for others the function is set by application pro-

gramcontrol.

· ExternalInterruptInput

The external interrupt pin, INT, is pin-shared with the

I/O pin PA5. To use the pin as an external interrupt in-

put the correct bits in the PA share pin option must be

selected. The pin must also be setup as an input by

setting the appropriate bit in the Port Control Register.

A pull-high resistor can also be selected via the appro-

priateportpull-highoption.

HT37B70 Datasheet(PDF) 21 Page - Holtek Semiconductor Inc

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