Universal Serial Interface Module - Usim; Spi Inte�Face - Holtek BS83B24C Manual

BS83B24C/BS83C40C
Touch Flash MCU
Universal Serial Interface Module – USIM
The devices contain a Universal Serial Interface Module, which includes the four-line SPI interface,
the two-line I C interface and the two-line UART interface types, to allow an easy method of
2
communication with external peripheral hardware. Having relatively simple communication
protocols, these serial interface types allow the microcontroller to interface to external SPI, I
UART based hardware such as sensors, Flash or EEPROM memory, etc. The USIM interface pins
are pin-shared with other I/O pins therefore the USIM interface functional pins must first be selected
using the corresponding pin-shared function selection bits. As all the interface types share the same
pins and registers, the choice of whether the UART, SPI or I
mode selection bit, named UMD, and the SPI/I
in the SIMC0 register. These pull-high resistors of the USIM pin-shared I/O are selected using pull-
high control registers when the USIM function is enabled and the corresponding pins are used as
USIM 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
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.
The SPI function in these devices offer the following features:
• Full duplex synchronous data transfer
• Both Master and Slave modes
• LSB first or MSB first data transmission modes
• Transmission complete flag
• Rising or falling active clock edge
The status of the SPI interface pins is determined by a number of factors such as whether the device
is in the master or slave mode and upon the condition of certain control bits such as CSEN and
SIMEN.
Rev. 1.00
C type is used is made using the UART
2
C operating mode control bits, named SIM2~SIM0,
2
C/UART function pins, the SPI interface pins
2
103
C or
2
�e���a�� 0�� �01�