H8SSLASH2225 datasheet(571/1071 Pages) RENESAS

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

Rev. 5.00 Aug 08, 2006 page 485 of 982

REJ09B0054-0500

(3) Communications Address

In the IEBus, a 12-bit specific communications addresses are allocated to individual units. A

communications address is configured as follows.

• Upper four bits: group number (number identifying a group to which the unit belongs)

• Lower eight bits: unit number (number identifying individual units in a group)

(4) Broadcast Communications

In normal transfer, a single master unit communicates with a single slave unit. So, one-to-one

transfer or reception is performed. In broadcast communications, a single master unit

communicates with multiple slave units. Since there are multiple slave units, acknowledgement is

not returned from the slave units during communications.

A broadcast bit decides whether broadcast or normal communications is performed. (For details of

the broadcast bit, see section 14.1.2 (1) (b), Broadcast Bit.

There are two types of broadcast communications.

(a) Group broadcast communications

Broadcast communications is performed to units with the same group number, meaning that

those units have the same upper four bits of the communications address.

(b) General broadcast communications

Broadcast communications is performed to all units regardless of the group number.

Group broadcast and general broadcast communications are identified by a slave address. (For

details on the slave address, see section 14.1.2 (3), Slave Address Field.)

14.1.2

Communications Protocol

Figure 14.2 shows an IEBus transfer signal format.

Communications data is transferred as a series of signals referred to as a communications frame.

The number of data which can be transmitted in a single communications frame and the transfer

speed differ according to communications mode.

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