H8S2258 Datasheet, PDF (571/1071 Pages) Renesas Technology Corp – 16-Bit Single-Chip Microcomputer H8S Family/H8S/2200 Series

Section 14 IEBus™ Controller (IEB) [H8S/2258 Group]
(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.
Rev. 5.00 Aug 08, 2006 page 485 of 982
REJ09B0054-0500