HT56R668 datasheet(53/104 Pages) HOLTEK

53 / 104 page

HT56R67/HT56R668/HT56C668/HT56R678/HT56C678/HT56R688

Rev. 1.20

March 4, 2010

A/D Transfer Function

As the device contain a 12-bit A/D converter, its

full-scale converted digitised value is equal to FFFH.

Since the full-scale analog input value is equal to the

VDD voltage, this gives a single bit analog input value of

VDD/4096. The diagram show the ideal transfer function

between the analog input value and the digitised output

value for the A/D converter.

Note that to reduce the quantisation error, a 0.5 LSB off-

set is added to the A/D Converter input. Except for the

digitised zero value, the subsequent digitised values will

change at a point 0.5 LSB below where they would

change without the offset, and the last full scale digitised

value will change at a point 1.5 LSB below the VDD level.

Serial Interface Function

The device contains a Serial Interface Function, which

includes both the four line SPI interface and the two line

2C interface types, to allow an easy method of commu-

nication with external peripheral hardware. Having rela-

tively simple communication protocols, these serial

interface types allow the microcontroller to interface to

external SPI or I

2C based hardware such as sensors,

Flash or EEPROM memory, etc. The SIM interface pins

are pin-shared with other I/O pins therefore the SIM in-

terface function must first be selected using a configura-

tion option. As both interface types share the same pins

and registers, the choice of whether the SPI or I

2C type

is used is made using a bit in an internal register.

SPI Interface

The SPI interface is often used to communicate with ex-

ternal peripheral devices such as sensors, Flash or

EEPROM memory devices etc. Originally developed by

Motorola, the four line SPI interface is a synchronous

serial data interface that has a relatively simple commu-

nication protocol simplifying the programming require-

ments when communicating with external hardware

devices.

The communication is full duplex and operates as a

slave/master type, where the MCU can be either master

or slave. Although the SPI interface specification can

control multiple slave devices from a single master,

here, as only a single select pin, SCS, is provided only

one slave device can be connected to the SPI bus.

· SPI Interface Operation

The SPI interface is a full duplex synchronous serial

data link. It is a four line interface with pin names SDI,

SDO, SCK and SCS. Pins SDI and SDO are the Serial

Data Input and Serial Data Output lines, SCK is the

Serial Clock line and SCS is the Slave Select line. As

the SPI interface pins are pin-shared with normal I/O

pins and with the I

2C function pins, the SPI interface

must first be enabled by selecting the SIM enable con-

figuration option and setting the correct bits in the

SIMCTL0/SIMCTL2 register. After the SPI configura-

tion option has been configured it can also be addi-

tionally disabled or enabled using the SIMEN bit in the

SIMCTL0 register. Communication between devices

connected to the SPI interface is carried out in a

slave/master mode with all data transfer initiations be-

ing implemented by the master. The Master also con-

trols the clock signal. As the device only contains a

single SCS pin only one slave device can be utilised.

The SPI function in this device offers the following fea-

tures:

¨ Full duplex synchronous data transfer

¨ Both Master and Slave modes

¨ LSB first or MSB first data transmission modes

¨ Transmission complete flag

F F E H

(

)

A / D C o n v e r s i o n

R e s u l t

F F F H

F F D H

0 3 H

0 2 H

0 1 H

0 . 5 L S B

4 0 9 3 4 0 9 4 4 0 9 5 4 0 9 6

A n a l o g I n p u t V o l t a g e

1 . 5 L S B

V D D

4 0 9 6

Ideal A/D Transfer Function

S P I M a s t e r

S P I S l a v e

S C K

S D O

S D I

S C S

S C K

S D I

S D O

S C S

SPI Master/Slave Connection

HT56R668 Datasheet(PDF) 53 Page - Holtek Semiconductor Inc

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