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Why does IRL interrupts are not detected when using SH-4 products?

Latest Updated:03/25/2009

Question:

When I am using the SH-4 products, sometimes IRL interrupts are not detected. Are there any possible reasons?

Answer:

The IRL interrupt is a level sense interrupt, and it is not retained in SH-4. Therefore it is possible to fail to take the interrupt under following condtions (a) or (b) during the IRL interrupt is input.

When it is the IRL interrupt, please assert the IRL interrupt signals until the interrupt request is accespted and withdraw the interrupt request (Inputting to IRL pins are negated) in the corresponding interrupt handler.

Condition:

(a) SR.BL bit is set to 1.

(b) The interrupt priority level from IRL pins is lower than the level of SR.IMASK bit.

Suitable Products
SH7760
SH7751R
SH7751
SH7750S
SH7750R