M32CSLASH8B datasheet(249/406 Pages) RENESAS

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Under development

M32C/8B Group

17. Serial Interfaces

Preliminary specification

Specifications in this manual are tentative and subject to change.

REJ09B0450-0050 Rev.0.50 Oct 31, 2008

Page 232 of 385

17.1.3.1 Detecting Start Condition and Stop Condition

The MCU detects the start condition and stop condition. The start condition detection interrupt request is

generated when the SDAi (i = 0 to 4) pin level changes from high (“H”) to low (“L”) while the SCLi pin level is

held “H”. The stop condition detection interrupt request is generated when the SDAi pin level changes from “L”

to “H” while the SCLi pin level is held “H”.

The start condition detection interrupt shares the Interrupt Control Register and interrupt vector with the stop

condition detection interrupt. The BBS bit in the UiSMR register determines which interrupt is requested.

Figure 17.25

Start Condition or Stop Condition Detection

17.1.3.2 Start Condition or Stop Condition Output

The start condition is generated when the STAREQ bit in the UiSMR4 register (i = 0 to 4) is set to 1 (start).

The restart condition is generated when the RSTAREQ bit in the UiSMR4 register is set to 1 (start).

The stop condition is generated when the STPREQ bit in the UiSMR4 is set to 1 (start).

The following is the procedure to output the start condition, restart condition, or stop condition.

(1) Set the STAREQ bit, RSTAREQ bit, or STPREQ bit to 1 (start).

(2) Set the STSPSEL bit in the UiSMR4 register to 1 (start/stop condition generation circuit selected).

Table 17.12 and Figure 17.26 show functions of the STSPSEL bit.

Table 17.12

STSPSEL Bit Function

Function

STSPSEL = 0

STSPSEL = 1

Output from pins SCLi and

SDAi

Output the serial clock and data.

Output of the start condition or stop

condition is controlled by software

utilizing port functions. (The start

condition and stop condition are not

automatically generated by hardware)

Output of the start condition or stop

condition is controlled by the status of bits

STAREQ, RSTAREQ, and STPREQ.

Timing to generate start

condition and stop condition

interrupt requests

When start condition and stop condition

are detected

When start condition and stop condition

generation are completed

i=0 to 4

NOTE:

1. These are cycles of the main clock oscillation frequency f(XIN).

SDAi

(stop condition)

6 cycles < setup time(1)

6 cycles < hold time(1)

Setup time

Hold time

SCLi

SDAi

(start condition)

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