R2023K datasheet(23/50 Pages) RICOH

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R2023K/T

• Transmission System of I2C-Bus

(1) Start Condition and Stop Condition

In I

2C-Bus, SDA must be kept at a certain state while SCL is at the “H” state during data transmission as shown

below.

SCL

SDA

tSU;DAT

tHD;DAT

The SCL and SDA pins are at the “H” level when no data transmission is made. Changing the SDA from “H” to “L”

when the SCL and the SDA are “H” activates the Start Condition and access is started. Changing the SDA from “L”

to “H” when the SCL is “H” activates Stop Condition and accessing stopped. Generation of Start and Stop

Conditions are always made by the master (see the figure below).

SCL

SDA

tHD;STA

tSU;STO

Start Condition

Stop Condition

(2) Data transmission and its acknowledge

After Start condition is entered, data is transmitted by 1byte (8bits).

Any bytes of data may be serially transmitted.

The receiving side will send an acknowledge signal to the transmission side each time 8bit data is transmitted.

The acknowledge signal is sent immediately after falling to “L” of SCL 8bit clock pulses of data is transmitted, by

releasing the SDA by the transmission side that has asserted the bus at that time and by turning SDA to “L” by

receiving side.

When transmission of 1byte data next to preceding 1byte of data is received the receiving side

releases the SDA pin at falling edge of the SCL 9bit of clock pulses or when the receiving side switches to the

transmission side it starts data transmission.

When the master is receiving side, it generates no acknowledge

signal after last 1byte of data from the slave to tell the transmitter that data transmission has completed.

The

slave side (transmission side) continues to release the SDA pin so that the master will be able to generate Stop

Condition, after falling edge of the SCL 9bit of clock pulses.

SCL

from the master

SDA from

the transmission side

SDA from

the receiving side

Acknowledge

signal

Start

Condition

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