HT68F20 datasheet(129/210 Pages) HOLTEK

129 / 210 page

HT68F20/HT68F30/HT68F40/HT68F50/HT68F60

Rev. 1.00

129

November 3, 2009

Serial Interface Module

- SIM

These devices contain a Serial Interface Module, which

includes both the four line SPI interface or 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 I2C type

is used is made using the SIM operating mode control

bits, named SIM2~SIM0, in the SIMC0 register. These

pull-high resistors of the SIM pin-shared I/O are se-

lected using pull-high control registers, and also if the

SIM function is enabled.

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 device can be either mas-

ter or slave. Although the SPI interface specification can

control multiple slave devices from a single master, but

this device provided only one SCS pin. If the master

needs to control multiple slave devices from a single

master, the master can use I/O pin to select the slave

devices.

· 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

SIMC0 and SIMC2 registers. After the SPI configura-

tion option has been configured it can also be addi-

tionally disabled or enabled using the SIMEN bit in the

SIMC0 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 utilized.

The SCS pin is controlled by software, set CSEN bit to

²1² to enable SCS pin function, set CSEN bit to ²0² the

SCS pin will be floating state.

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

D a t a B u s

S D I P i n

S D O P i n

S I M D

T x / R x S h i f t R e g i s t e r

B u s y

S t a t u s

C o n f i g u r a t i o n

O p t i o n

T R F F l a g

E n a b l e / D i s a b l e

W C O L F l a g

C l o c k

E d g e / P o l a r i t y

C o n t r o l

C l o c k

S o u r c e S e l e c t

f S Y S

f T B C

T M 0 C C R P m a t c h f r e q u e n c y / 2

S C K P i n

S C S P i n

C o n f i g u r a t i o n

O p t i o n

C S E N b i t

E n a b l e / D i s a b l e

C K E N b i t

C K P O L B b i t

SPI Block Diagram

HT68F20 Datasheet(PDF) 129 Page - Holtek Semiconductor Inc

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