H8SSLASH2225 datasheet(576/1071 Pages) RENESAS

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Section 14 IEBus™ Controller (IEB) [H8S/2258 Group]

Rev. 5.00 Aug 08, 2006 page 490 of 982

REJ09B0054-0500

(6) Data Field

The data field is a field for data transmission/reception to the slave unit. The master unit

transmits/receives data to/from the slave unit using the data field. The data field is comprised of

data bits, a parity bit, and an acknowledge bit.

The data bits include eight bits and are output MSB first.

The parity bit and acknowledge bit following the data bits are output from the master unit and

slave unit, respectively.

Broadcast communications are performed only for the transmission of the master unit. In this case,

the acknowledge bit is ignored. Operations in master transmission and master reception are

described below.

(a) Master Transmission

The master unit transmits the data bits and parity bit to the slave unit to write data from the

master unit to the slave unit. The slave unit receives the data bits and parity bit, and returns the

acknowledgement if the parity bit is correct and the receive buffer is empty. If the parity bit is

not correct or the receive buffer is not empty, the slave unit rejects acceptance of

corresponding data and does not return the acknowledgement.

When the slave unit does not return the acknowledgement, the master unit retransmits the same

data. This operation is repeated until either the acknowledgement from the slave unit is

detected or the maximum number of data transfer bytes is exceeded.

When the parity is correct and the acknowledgement is output from the slave unit, the master

unit transmits the subsequent data if data remains and the maximum number of transfer bytes

is not exceeded.

In the case of broadcast communications, the slave unit does not return the acknowledgement,

and the master unit transfers data byte by byte.

(b) Master Reception

The master unit outputs synchronous signals corresponding to all data bits to be read from the

slave unit.

The slave unit outputs the data bits and parity bit on the bus in accordance with the

synchronous signals from the master unit.

The master unit reads the parity bit output from the slave unit, and checks the parity. If the

parity is not correct, or the receive buffer is not empty, the master unit rejects acceptance of the

data, and does not return the acknowledgement. The master unit reads the same data repeatedly

if the number of data does not exceed the maximum number of transfer bytes in one frame. If

the parity is correct and the receive buffer is empty, the master unit accepts data and returns the

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