Usage Notes; Module Stop Mode Setting - Renesas H8S/2100 Series Hardware Manual

6-bit single-chip microcomputer

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Table of Contents

Section 18 SMBus 2.0 Interface (SMBUS)

Write transmit/receive

Transmit/receive PEC

1. Initialize the PEC calculation module before starting transmission or reception. Use a word-

transfer instruction to write H'0000 to both PECX and PECY, or use byte-transfer instructions

to write H'00 to PECX and then PECY.

2. Write transmit data or receive data to PECX in byte units each time a byte of an address or

data is received or transmitted. However, do not write data to PECY during PEC calculation.

3. After writing the last transmit/receive data to PECX, read PECZ to obtain the result of PEC

calculation.

4. For data transmission, transmit the result of PEC calculation.

5. For data reception, compare the received PEC data with the result of PEC calculation. If the

data match, successful reception has been confirmed.

Usage Notes

The SMBUS operation can be enabled or disabled using the module stop control register. The

initial setting is for the SMBUS operation to be halted. Register access is enabled by canceling

module stop mode. For details, see section 26, Power-Down Modes.

Rev. 1.00 May 09, 2008 Page 552 of 954

REJ09B0462-0100

[1] Write H'0000 to PECX and PECY.

Initial setting

[2] Write transmit/receive data on which PEC calculation

is required to PECX (byte units).

data to PECX

[3] Read PECZ after the PEC calculation of the last

transmit/receive data.

[4] For data transmission, transmit the value in PECZ.

[5] For data reception, compare the received PEC data

with the value in PECZ.

Figure 18.4 Sample Flowchart of PEC Calculation