HT45F65 Datasheet, PDF (154/231 Pages) Holtek Semiconductor Inc – Glucose Meter 8-Bit Flash MCU

HT45F65/HT45F66/HT45F67
Glucose Meter 8-Bit Flash MCU
Serial Interface Module – SIM
The devices contain a Serial Interface Module, which includes both the four line SPI interface and
the two line I²C 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 I²C based hardware such as sensors, Flash memory,
etc. The SIM interface pins are pin-shared with other I/O pins therefore the SIM interface function
must first be selected using a configuration 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 selected using pull-high control registers, and also if the SIM function is enabled.
SPI Interface
This SPI interface function which is contained within the Serial Interface Module, should not be
confused with the other independent SPI function, known as SPI1, which is described in another
section of this datasheet. The SPI interface is often used to communicate with external peripheral
devices such as sensors, Flash 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 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 I²C function pins, the SPI interface must first be enabled by
selecting the SIM enable configuration option and setting the correct bits in the SIMC0 and SIMC2
registers. After the SPI configuration option has been configured 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 P I M a s te r
SCK
S P I S la v e
SCK
SDO
SDI
SDI
SDO
SCS
SCS
SPI Master/Slave Connection
Rev. 1.60
154
November 24, 2015