Holtek HT66F20-1 Manual page 145

HT66F20-1/HT66F30-1/HT68F20-1/HT68F30-1
Flash MCU with EEPROM
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 other functions and with the I
be selected by the correct bits in the SIMC0 and SIMC2 registers. After the SPI option has been
selected, it can also be additionally 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 being implemented by the master. The Master also controls
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 "1" to enable SCS pin function, set CSEN bit
to "0" the SCS pin will be floating state.
S C K P i n
T M 0 C C R P m a t c h f r e q u e n c y / 2
S C S P i n
Rev. 1.40
S P I M a s t e r
S C K
S D O
S D I
S C S
SPI Master/Slave Connection
S I M D
T x / R x S h i f t R e g i s t e r
C l o c k
C K E G b i t
E d g e / P o l a r i t y
C K P O L B b i t
C o n t r o l
f
S Y S
C l o c k
f
T B C
S o u r c e S e l e c t
C o n f i g u r a t i o n
C S E N b i t
O p t i o n
E n a b l e / D i s a b l e
SPI Bolck Diagram
145
C function pins, the SPI interface must first
2
S P I S l a v e
S C K
S D I
S D O
S C S
D a t a B u s
S D I P i n
S D O P i n
E n a b l e / D i s a b l e
B u s y
C o n f i g u r a t i o n
S t a t u s
O p t i o n
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W C O L F l a g
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