SH7261 datasheet(331/1348 Pages) RENESAS

331 / 1348 page

Section 10 Bus Monitor

Rev. 2.00 Sep. 07, 2007 Page 299 of 1312

REJ09B0320-0200

10.2

Bus Monitor Function

The bus monitor function detects two types of bus error: illegal address access and bus timeout.

Bus error detection is performed in one bus access.

Even when data is transferred in multiple bus accesses such as burst transfer, a bus error can be

detected in one bus access.

10.2.1

Operation when a Bus Error is Detected

When a bus error is detected, the status is saved in the bus monitor status register 1 (SYCBESTS1)

and bus monitor status register 2 (SYCBESTS2) and the CPU is notified of the bus error is

notified to the CPU.

(1)

Saving Status in Bus Monitor Status Register or Bus Monitor Status Register 2

When a bus error occurs, the status at the time (what type of error occurred and which bus was

being accessed by which bus master) is saved in the bus monitor status register 1 (SYCBESTS1)

or bus monitor status register 2 (SYCBESTS2).

Even if another bus error occurs after this, the value in the bus monitor status register

(SYCBESTS) or bus monitor status register 2 (SYCBESTS2) is not updated. When multiple bus

errors occur at the same time, multiple status bits may be set.

The bus monitor status register 1 (SYCBESTS1) or bus monitor status register 2 (SYCBESTS2)

can be cleared by writing 1 to the status clear bit (STSCLR) in the bus monitor enable register

(SYCBEEN) from the bus master. After being cleared, the status of a bus error, if generated, is

saved in the bus monitor status register 1 (SYCBESTS1) or bus monitor status register 2

(SYCBESTS2) again.

When a clear operation and a bus error happen at the same time, the clear operation has priority

and the bus error is ignored.

SH7261 Datasheet(PDF) 331 Page - Renesas Technology Corp