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