Introduction; Z8 Addressing Modes - ZiLOG Z8 User Manual

11.1 INTRODUCTION

11.1.1 Z8 Addressing Modes

The Z8 microcontroller provides six addressing modes:
• Register (R)
• Indirect Register (IR)
• Indexed (X)
• Direct (D)
• Relative (RA)
• Immediate (IM)
With the exception of immediate data and condition codes, all
operands are expressed as register file, Program Memory, or
Data Memory addresses. Registers are accessed using 8-bit ad-
dresses in the range of 00H-FFH. The Program Memory or Data
Memory is accessed using 16-bit addresses (register pairs) in the
range of 0000H-FFFFH.
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Working Registers are accessed using 4-bit addresses in the
range of 0-15 (0H-FH). The address of the register being access-
ed is formed by the combination of the upper four bits in the Reg-
ister Pointer (R253) and the 4-bit working register address sup-
plied by the instruction.
Registers can be used in pairs to designate 16-bit values or mem-
ory addresses. A Register Pair must be specified as an even-num-
bered address in the range of 0, 2,...., 14 for Working Registers,
or 4, 6,....238 for actual registers.
In the following definitions of Z8 Addressing Modes, the use
of'register' can also imply register pair, working register, or
working register pair, depending on the context.
Note: See the product data sheet for exact program, data, and
register memory types and address ranges available.
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