H8SSLASH2224 datasheet(573/1071 Pages) RENESAS

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

Rev. 5.00 Aug 08, 2006 page 487 of 982

REJ09B0054-0500

When more than one unit starts transfer of communications frame at the same timing,

broadcast communications has priority over normal communications, and arbitration occurs.

(2) Master Address Field

The master address field is a field for transmitting the unit address (master address) to other units.

The master address field is comprised of master address bits and a parity bit.

The master address has 12 bits and are output MSB first.

When more than one unit starts transfer of the broadcast bit having the same value at the same

timing, arbitration is decided by the master address field.

In the master address field, self-output data and data on the bus are compared for every one-bit

transfer. If the self-output master address and data on the bus are different, the unit that loses

arbitration, stops transfer, and enters the receive state.

Since the IEBus is configured with wired AND, a unit having the smallest master address of the

units in arbitration (arbitration master) wins in arbitration.

Finally, only a single unit remains in the transfer state as a master unit after outputting 12-bit

master address.

Next, this master unit outputs a parity bit*, defines the master address to other units, and then

enters the slave address field output state.

Note: * Since even parity is used, when the number of one bits in the master address is odd, the

parity bit is 1.

(3) Slave Address Field

The slave address field is a field to transmit an address (slave address) of a unit (slave unit) to

which a master transmit data. The slave address field is comprised of slave address bits, a parity

bit, and an acknowledge bit.

The slave address has 12 bits and is output MSB first. The parity bit is output after the 12-bit slave

address is transmitted in order to avoid receiving the slave address accidentally. The master unit

then detects the acknowledgement from the slave unit in order to confirm that the slave unit exists

on the bus. When the acknowledgement is detected, the master unit enters the control field output

state. However, the master unit enters the control field output state without detecting the

acknowledgement in broadcast communications.

H8S/2224 Scheda tecnica(PDF) 573 Page - Renesas Technology Corp