Jameco Electronics 2000, 3000 manual Computed Long Calls and Jumps

Models: 3000 2000

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3.5.6 Computed Long Calls and Jumps

3.5.6 Computed Long Calls and Jumps

The instruction to set the XPC is privileged to so that a computed long call or jump can be made. This would be done by the following sequence.

LD xpc,a

JP (HL)

In this case, A has the new XPC, and HL has the new PC. This code should normally be executed in the root segment so as not to pull the memory out from under the JP (HL) instruction.

A call to a computed address can be performed by the following code.

;A=xpc, IY=address

LD A,newxpc

LD IY,newaddress

 

LCALL DOCALL

;

call utility routine in the root

;

;The DOCALL routine

DOCALL:

LD

xpc,a

;

SET xpc

JP

(IY)

;

go to the routine

48

Rabbit 3000 Microprocessor

Page 57
Image 57
Jameco Electronics 2000, 3000 manual Computed Long Calls and Jumps