Epson RTC-8564JE Applications Manual

RTC - 8564 JE/NBPage - 8 MQ - 322 - 048.3. Access procedure8.3.1. Characteristic of the I 2 C-BUSI 2 C-BUS is a bi-directional interface that uses two (2) lines. This interface has two signal lines, which are SDA (dataline) and SCL (clock line). Both of these lines are connected to the V DD line via the pull-up registers. All ports must beopen drain or open collector on the I 2 C-BUS in order to be able to connect multiple devices on this bus using theAND-connection.8.3.2. Bit transferThe bit data transfer is executed for one bit on each one clock pulse of SCL line. When the device transmits the data,the data change should be executed while SCL line is at LOW. When the device receives the data, the data should betaken in while SCL is at HIGH.8.3.3. Start condition and stop conditionWhen I 2 C-BUS is not interfacing, the two control lines keep at HIGH. When SDA changes from HIGH to LOW, this isdefined as a start condition. After that, actual data transfer is executed. When SCL is at HIGH and when SDA changesfrom LOW to HIGH, this is defined as a stop condition.SDASCLS PStart condition Stop condition8.3.4. Slave addressThe I 2 C-BUS devices do not have any chip select pins with the usual logic devices. All I 2 C-BUS devices have a fixedunique device number for each device built into them. The chip selection on the I 2 C-BUS is executed when thecommunication starts and this device number is sent from I 2 C-BUS as a slave address. The receiving device respondsto the communication only if it matches the slave address.The slave address is a 7-bit data which is made of a 4-bit fixed data (group 1) and 3-bits data (group 2). On theRTC-8564, the data in group 1 is 1010 and in group 2 is 001.∗1) RTC-8564 slave address 1 0 1 0 0 0 1Group 1 Group 2∗2) During the actual data transmission,the transmitted data contains both theslave address and the 8-bit data withthe added R/W (read/write) bit.Slave address R/Wbitbit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 01 0 1 0 0 0 1 R/W0 ; when write mode1 ; when read mode