HD64F2149YV datasheet(580/1075 Pages) RENESAS

580 / 1075 page

Section 16 I

2C Bus Interface

Rev. 3.00 Jan 18, 2006 page 552 of 1044

REJ09B0280-0300

• Notes on ICDR Reads and ICCR Access in Slave Transmit Mode

In a transmit operation in the slave mode of the I

2C bus interface, do not read the ICDR register

or read or write to the ICCR register during the period indicated by the shaded portion in figure

16.22.

Normally, when interrupt processing is triggered in synchronization with the rising edge of the

9th clock cycle, the period in question has already elapsed when the transition to interrupt

processing takes place, so there is no problem with reading the ICDR register or reading or

writing to the ICCR register.

To ensure that the interrupt processing is performed properly, one of the following two

conditions should be applied.

(1) Make sure that reading received data from the ICDR register, or reading or writing to the

ICCR register, is completed before the next slave address receive operation starts.

(2) Monitor the BC2 to BC0 counter in the ICMR register and, when the value of BC2 to BC0

is 000 (8th or 9th clock cycle), allow a waiting time of at least 2 transfer clock cycles in

order to involve the problem period in question before reading from the ICDR register, or

reading or writing to the ICCR register.

SDA

R/W

Waveforms if

problem occurs

Bit 7

ICDR write

Data transmission

Period when ICDR reads and ICCR

reads and writes are prohibited

(6 system clock cycles)

Detection of 9th clock

cycle rising edge

SCL

TRS

Address received

Figure 16.22 ICDR Read and ICCR Access Timing in Slave Transmit Mode

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