AN1042 Ver la hoja de datos (PDF) - STMicroelectronics
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AN1042 Datasheet PDF : 8 Pages
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ST7 ROUTINE FOR I2C SLAVE MODE MANAGEMENT
2 ST7 I2C COMMUNICATION APPLICATION
2.1 HARDWARE CONFIGURATION
The ST7 I2C communication application hardware is composed by a ST72264 microcontroller
used as a slave which communicates with any master through an I2C bus interface.
Figure 3. ST7 I2C Communication Application
ST72F264 Vdd
SCL
I2C
SDA
5V
2x100Ω
2x27KΩ
master
SCL
Vdd
SDA
Vss
Vss
2.2 ST7 I2C PERIPHERAL BASIC DRIVERS
In this chapter all registers refer to the ST7 I2C peripheral ones (otherwise specified).
2.2.1 Initialize the I2C peripheral
In this application the initialization of the ST7 I2C peripheral is done completely by software.
First the Control register (CR) is cleared and the Data (DR) and Status (SR1,SR2) registers
are touched to clear all possible pending event.
Then, the peripheral is enabled through the Control register (CR). This action needs to write
twice in the register due to the fact that the Control register (CR) bits can be set only when the
PE enable bit is already set. To allow the peripheral to acknowledge the received data the
ACK bit of the Control register (CR) is set.
2.2.2 Slave Communication on the I2C Bus
First the interface frequency must be configured using the FRi bits in the OAR2 register.For
10 bit addressing mode, user must configure the slave address using the ADD9 and ADD8
bits of the OAR2 register.
To initiate a I2C communication, first a start condition has to be generated and then the se-
lected slave address has to be sent, both by the master. As soon as a start condition is de-
tected, the address is received from the SDA line and sent to the shift register; then it is com-
pared with the address of the interface (OAR1) or the General Call address (if selected by soft-
ware). If the GCAL option is to be implemented, user must enable it by selecting the
GCAL_Add in user customizable part of the code.
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