H8SSLASH2224 datasheet(581/1071 Pages) RENESAS

581 / 1071 page

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

Rev. 5.00 Aug 08, 2006 page 495 of 982

REJ09B0054-0500

(2) Data Command Transfer (Control Bits: Read (H'3, H'7), Write (H'A, H'B, H'E, H'F))

In the case of data read (H'3, H'7), data in the data buffer of the slave unit is read in the master

unit. In the case of data write (H'B or H'F) or command write (H'A or H'E), data received in the

slave unit is processed in accordance with the operation specification of the slave unit.

Notes: 1. The user can select data and commands freely in accordance with the system.

2. H'3, H'A, or H'B may lock depending on the communications condition and status.

(3) Locked Address Read (Control Bits: H'4, H'5)

In the case of the locked address read (H'4 or H'5), the address (12 bits) of the master unit which

issues lock instruction is configured in bytes shown in figure 14.4.

MSB

Lower 8 bits

Undefined

Control bits: H'4

Control bits: H'5

Upper 4 bits

LSB

Figure 14.4 Locked Address Configuration

(4) Locking/Unlocking (Control Bits: Setting (H'3, H'A, H'B), Cancellation: (H'6))

The lock function is used for message transfer over multiple communications frames. Locked unit

receives data only from the unit which has locked.

Locking and unlocking are described below.

• Locking

When the acknowledge bit of 0 in the message length field is transmitted/received with the

control bits indicating the lock operation, and then the communications frame is completed

before completion of data transmission/reception for the number of bytes specified by the

message length bits, the slave unit is locked by the master unit. In this case, the bit (bit 2)

relevant to lock in the byte data indicating the slave status is set to 1.

Lock is set only when the number of data exceeds the maximum number of transfer bytes in

one frame. Lock is not set by other error termination.

• Unlocking

When the control bits indicate the lock (H'3, H'A, or H'B) or unlock (H'6) operation and the

byte data for the number of bytes specified by the message length bits are transmitted/received

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