Call Int 13h in a ISR

I have written a ISR for int 9h by assembly in Real Mode. In this ISR, I call INT 13h, AH=0x02 for writing some data on Hard Disk. But data aren't written on Hard Disk. Also int 13h, ah=0x02 doesn't work too (Read data from Hard Disk). after call int 13h, Carry Flag is On, but AH and AL are zero. When I 开发者_如何学JAVAuse this code out of ISR, it's work! Why INT13h in a ISR doesn't work, but other interrupt, for example INT10h work correctly?

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The simple answer is thatint 13hwill not complete successfully without the hard drive hardware interrupt IRQ 5 -int 0Dhwhich will not occur until the PIC is acknowleged at the end of keyboard hardware interrupt IRQ 1 -int 9h.

The happy answer is that it is much simpler to use int 16h ah=0 to wait for a keypress.