HT56R666 View Datasheet(PDF) - Holtek Semiconductor
Part Name
Description
MFG CO.
'HT56R666' PDF : 104 Pages View PDF
HT56R66/HT56R666
CKPOL
0
CKEG
0
0
1
1
0
1
1
SCK Clock Signal
High Base Level
Active Rising Edge
High Base Level
Active Falling Edge
Low Base Level
Active Falling Edge
Low Base Level
Active Rising Edge
SPI Communication
After the SPI interface is enabled by setting the SIMEN
bit high, then in the Master Mode, when data is written to
the SIMDR register, transmission/reception will begin si-
multaneously. When the data transfer is complete, the
TRF flag will be set automatically, but must be cleared
using the application program. In the Slave Mode, when
the clock signal from the master has been received, any
data in the SIMDR register will be transmitted and any
data on the SDI pin will be shifted into the SIMDR regis-
ter. The master should output an SCS signal to enable
the slave device before a clock signal is provided and
slave data transfers should be enabled/disabled be-
fore/after an SCS signal is received.
The SPI will continue to function even after a HALT in-
struction has been executed.
I2C Interface
The I2C interface is used to communicate with external
peripheral devices such as sensors, EEPROM memory
etc. Originally developed by Philips, it is a two line low
speed serial interface for synchronous serial data trans-
fer. The advantage of only two lines for communication,
relatively simple communication protocol and the ability
to accommodate multiple devices on the same bus has
made it an extremely popular interface type for many
applications.
· I2C Interface Operation
The I2C serial interface is a two line interface, a serial
data line, SDA, and serial clock line, SCL. As many
devices may be connected together on the same bus,
their outputs are both open drain types. For this rea-
son it is necessary that external pull-high resistors are
connected to these outputs. Note that no chip select
line exists, as each device on the I2C bus is identified
by a unique address which will be transmitted and re-
ceived on the I2C bus.
When two devices communicate with each other on
the bidirectional I2C bus, one is known as the master
device and one as the slave device. Both master and
slave can transmit and receive data, however, it is the
master device that has overall control of the bus. For
these devices, which only operates in slave mode,
there are two methods of transferring data on the I2C
bus, the slave transmit mode and the slave receive
mode.
S T A R T s ig n a l
fro m M a s te r
S e n d s la v e a d d r e s s
a n d R /W b it fr o m M a s te r
A c k n o w le d g e
fr o m s la v e
S e n d d a ta b y te
fro m M a s te r
A c k n o w le d g e
fr o m s la v e
S T O P s ig n a l
fro m M a s te r
There are several configuration options associated
with the I2C interface. One of these is to enable the
function which selects the SIM pins rather than normal
I/O pins. Note that if the configuration option does not
select the SIM function then the SIMEN bit in the
SIMCTL0 register will have no effect. A configuration
option exists to allow a clock other than the system
clock to drive the I2C interface. Another configuration
option determines the debounce time of the I2C inter-
face. This uses the internal clock to in effect add a
debounce time to the external clock to reduce the pos-
sibility of glitches on the clock line causing erroneous
operation. The debounce time, if selected, can be
chosen to be either 1 or 2 system clocks.
SIM
Function
SIM function
I2C clock
SIM interface or SEG pins
I2C runs without internal clock
Disable/Enable
I2C debounce
No debounce, 1 system clock;
2 system clocks
I2C Interface Configuration Options
· I2C Registers
There are three control registers associated with the
I2C bus, SIMCTL0, SIMCTL1 and SIMAR and one
data register, SIMDR. The SIMDR register, which is
shown in the above SPI section, is used to store the
data being transmitted and received on the I2C bus.
Before the microcontroller writes data to the I2C bus,
the actual data to be transmitted must be placed in the
SIMDR register. After the data is received from the I2C
bus, the microcontroller can read it from the SIMDR
register. Any transmission or reception of data from
the I2C bus must be made via the SIMDR register.
Note that the SIMAR register also has the name
SIMCTL2 which is used by the SPI function. Bits
SIMIDLE , SIMEN and bits SIM0~SIM2 in register
SIMCTL0 are used by the I2C interface. The SIMCTL0
register is shown in the above SPI section.
Rev. 1.40
60
May 11, 2012
Share Link: 
