PD72042B_15 datasheet(13/92 Pages) RENESAS

13 / 92 page

µPD72042B

Data Sheet S13990EJ3V0DS

2.2.3

Communication Address

With the IEBus, each device is assigned a unique 12-bit communication address. The communication address

consists of the following parts:

High-order 4 bits

: Group number (number identifying the group to which a device belongs)

Low-order 8 bits

: Unit number (number identifying a device in a group)

2.2.4

Broadcast

In ordinary communication, transmission and reception are performed between one master unit and one associated

slave unit. Broadcast can also be done between one master unit and more than one slave unit. In this case master

unit transmits data to an arbitrary number of slave units. In this case, the slave units do not return on acknowledge

signal to the master unit.

Whether the communication to be performed is broadcast or ordinary communication is determined by the setting

of the broadcast bit. (For details of the broadcast bit, see (1) 2 in Section 2.3.)

There are two types of broadcast.

(1) Group broadcast

Broadcast is performed to the devices in a particular group. These devices all have the same group number,

as indicated by the high-order 4 bits of each communication address.

(2) General broadcast

Broadcast is performed to all devices, regardless of their group numbers.

These two types of broadcast are distinguished by the slave address. (For details of the slave address, see (3)

in Section 2.3.)

2.3

TRANSMISSION PROTOCOL

Fig. 2-1 shows the IEBus transmission signal format.

Communication data is transmitted as a sequence of signals called a communication frame. The transmission

speed and the maximum amount of data that can be transmitted in one communication frame depend on the

communication mode.

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