z80_AS(1)

NAME
z80_as - assembler for Zilog z80

SYNOPSIS
/usr/em/lib/z80_as [options] argument ...

DESCRIPTION
This assembler is made with the general framework described in uni_ass(6).

SYNTAX

registers
    The z80 has six general-purpose 8-bit registers: b, c, d, e, h, l; an 8-bit accumulator: a; an 8-bit flag register: f; an 8-bit interrupt vector: i; an 8-bit memory refresh register: r; two 16-bit index registers: ix, iy; a 16-bit stack pointer: sp; and a 16-bit program counter: pc. The general-purpose registers can be paired to form three registers pairs of 16 bits each: bc, de, hl. An alternate set of registers is provided that duplicates the accumulator, the flag register, and the general-purpose registers. The "exx"-instruction exchanges the contents of the two sets of general-purpose registers; the contents of the accumulator and flag register can be exchanged with the contents of their alternates by the "ex af, af2"-instruction.

addressing modes
    syntax		meaning
    expr		dependent on the instruction, the
    		value of `expr' can be immediate
    		data or the address of the operand.
    		There is no special notation for
    		immediate data.
    (ireg + expr)
    (ireg - expr)	the contents of ireg (which must be
    		one of the index-registers) + or -
    		the - one byte - value of `expr'
    		yield the address of the operand.
    (expr)		the value of `expr' is the address of
    		the operand.
    reg		the contents of `reg' - one of the above-
    		mentioned registers - is the operand.
    (reg)		the contents of `reg' - one of the 16-bit
    		registers except pc - is the address of
    		the operand.
    nz, z, nc, c,
    po, pe, p, m	the letters indicate a condition-code:
    		nonzero, zero, carry, no carry,
    		parity odd, parity even, sign positive,
    		sign negative respectively. Used by conditional
    		jump, call, and return instructions.

instructions
    The jr-instruction will automatically be replaced by a jp-instruction if the target is too remote.

SEE ALSO
uni_ass(6), ack(1),
Z80 Users Manual, Joseph J. Carr, Reston Publishing Company, 1980