H8SSLASH2224 datasheet(570/1071 Pages) RENESAS

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

Rev. 5.00 Aug 08, 2006 page 484 of 982

REJ09B0054-0500

(a) Priority according to communications type

Broadcast communications (one-to-many communications) has priority over normal

communications (one-to-one communications).

(b) Priority according to master address

A unit with the smallest master address has priority among units with the same

communications type.

Example: The master address is configured with 12 bits. A unit with H'000 has the highest

priority, and a unit with H'FFF has the lowest priority.

Note: When a unit loses arbitration, the unit can automatically enter retransfer mode (0 to 7

retransfer times can be selected by bits RN2 to RN0 in IEMCR).

(2) Communications Mode

The IEBus has three communications modes with different transfer speeds. Table 14.2 shows the

transfer speed in each communications mode and the maximum number of transfer bytes in one

communications frame.

Table 14.2 Transfer speed and Maximum Number of Transfer Bytes in Each

Communications Mode

Effective Transfer Speed*

1 (kbps)

Communications

Mode

Maximum Number

of Transfer Bytes

(byte/frame)

φφφφ = 12 MHz*

φφφφ = 12.58 MHz*

About 3.9

About 4.1

About 17

About 18

128

About 26

About 27

Notes:

Each unit connected to the IEBus should select a communications mode prior to

performing communications. Note that correct communications is not guaranteed if the

master and slave units do not adopt the same communications mode.

In the case of communications between a unit with

φ = 12 MHz and a unit with φ =

12.58 MHz, correct communications is not possible even if the same communications

mode is adopted. Communications must be performed at the same oscillation

frequency.

1. An effective transfer speed when the maximum number of transfer bytes is transmitted.

2. Oscillation frequency when this LSI is used

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