Rabbit 2000 Reference Manual

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42 Rabbit 2000/3000 MicroprocessorDescriptionThis instruction is similar to the CALL routine in that it transfers program execution to the subroutine addressspecified by the 16-bit operand mn. The LCALL instruction is special in that it allows calls to be made to acomputed address in XMEM. Note that the value of XPC and consequently the address space defined by theXPC is dynamically changed with the LCALL instructions.In the LCALL instruction, first the Extension of the Program Counter, XPC, is pushed onto the stack. Nextthe Program Counter, PC, is pushed onto the stack, the high order byte first, then the low order byte. Then theXPC is loaded with the 8-bit value x and the PC is loaded with the 16-bit value, mn. The Stack Pointer registeris then updated to reflect the three items pushed onto it.The value mn must be in the range E000–FFFF.This instruction is implemented for the Rabbit and is not available for the Z180.Alternate FormsThe Dynamic C assembler recognizes several other forms of this instruction.LCALL labelLCALL x,labelLCALL x:labelLCALL x:mnThe parameter label is a user defined label. The colon is equivalent to the comma as a delimiter.LCALL x,mnOpcode Instruction Clocks OperationCF n m x LCALL x,mn 19 (2,2,2,2,1,3,3,3,1) (SP - 1) = PC (low);(SP - 2) = PC (high);(SP - 3) = XPC;XPC = x;PC = mn;SP = SP - 3Flags ALTD I/OS Z L/V C F R SP S D- - - -