Sharp MZ-80B Owner's Manual page 93

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4.0 INSTRUCTION SET
The Z-80A CPU can execute 15 8 different instruction types including all 78 of the 8080A CPU. The instructions
can be broken down into the following major groups:
• Load and Exchange
• Block Transfer and Search
• Arithmetic and Logical
• Rotate and Shift
• Bit Manipulation (set, reset, test)
• Jump, Call and Return
• Input/Output
• Basic CPU Control
4.1 INTRODUCTION TO INSTRUCTION TYPES
The load instructions move data internally between CPU registers or between CPU registers and external memory .
All of these instructions must specify a source location from which the data is to be moved and a destination location.
The source location is not altered by a load instruction. Examples of load group instructions include moves between
any of the general purpose registers such as move the data to Register B from Register C. This group also includes load
immediate to any CPU register or to any to Register B from Register C. This group also includes load immediate to any
CPU register or to any external memory location. Other types of load instructions allow transfer between CPU registers
and memory locations. The exchange instructions can trade the contents of two registers.
A unique set of block transfer instructions is provided in the Z-80A. With a single instruction a block of memory of
any size can be moved to any other location in memory . This set of block moves is extremely valuable when large
strings of data must be processed. The Z-80A block search instructions are also valuable for this type of processing.
With a single instruction, a block of external memory of any desired length can be searched for any 8-bit character.
Once the character is found or the end of the block is reached , the instruction automatically terminates. Both the block
transfer and the block search instructions can be interrupted during their execution so as to not occupy the CPU for
long periods of time.
The arithmetic and logical instructions operate on data stored in the accumulator and other general purpose CPU
registers or external memory locations. The results of the operations are placed in the accumulator and the appropriate
flags are set according to the result of the operation. An example of an arithmetic operation is adding the accumulator
to the contents of an external memory location. The results of the addition are placed in the accumulator. This group
also includes 16-bit addition and subtraction between 16-bit CPU registers.
The rotate and shift group allows any register or any memory location to be rotated right or left with or without
carry either arithmetic or logical. Also, a digit in the accumulator can be rotated right or left with two digits in any
memory location.
The bit manipulation instructions allow any bit in the accumulator, any general purpose register or any external
memory location to be set, reset or tested with a single instruction. For example, the most significant bit of register H
can be reset. This group is especially useful in control applications and for controlling software flags in general purpose
programming.
The jump, call and return instructions are used to transfer between various locations in the user's program. This
group uses several different techniques for obtaining the new program counter address from specific external memory
locations. A unique type of call is the restart instruction. This instruction actually contains the new address as a part of
the 8-bit OP code. This is possible since only 8 separate addresses located in page zero of the external memory may be
specified. Program jumps may also be achieved by loading register HL, IX or IY directly into the PC, thus allowing the
jump address to be a complex function of the routine being executed.