Rev. 1.00
132
September 11, 2018
Rev. 1.00
133
September 11, 2018
HT45F4050
A/D NFC Flash MCU
HT45F4050
A/D NFC Flash MCU
Serial Interface Module – SIM
The device contains a Serial Interface Module, which includes both the four line SPI interface and
the two line I
2
C interface types, to allow an easy method of communication with external peripheral
hardware. Having relatively simple communication protocols, these serial interface types allow
the microcontroller to interface to external SPI or I
2
C 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
interface functional pins must first be selected using the corresponding pin-shared function selection
bits. As both interface types share the same pins and registers, the choice of whether the SPI or I
2
C
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 selected using pull-high control
registers when the SIM function is enabled and the corresponding pins are used as SIM input pins.
SPI Interface
The SPI interface is often used to communicate with external 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 communication protocol
simplifying the programming requirements when communicating with external hardware devices.
The communication is full duplex and operates as a slave/master type, where the device can be either
master or slave. Although the SPI interface specification can control multiple slave devices from a
single master, but the device provides 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, the SCK
pin
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
2
C function pins, the SPI interface pins must first
be selected by configuring the pin-shared function selection bits and setting the correct bits in the
SIMC0 and SIMC2 registers. 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.
SCK
SPI Master
SDO
SDI
SCS
SCK
SPI Slave
SDI
SDO
SCS
SPI Master/Slave Connection