Z89321 datasheet(35/40 Pages) ZILOG

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Z89321/371/391

Zilog

16-Bit Digital Signal Processors

DS97DSP0100

P R E L I M I N A R Y

There are eight distinct addressing modes for data trans-

fer.

<pregs>, <hwregs> These two modes are used for sim-

ple loads to and from registers within the chip, such as

loading to the Accumulator, or loading from a pointer reg-

ister. The names of the registers need only be specified in

the operand field (destination first, then source).

<regind> This mode is used for indirect accesses to the

data RAM. The address of the RAM location is stored in

the pointer. The Ò@Ó symbol indicates ÒindirectÓ and pre-

cedes the pointer, therefore @P1:1 instructs the processor

to read or write to a location in RAM1, which is specified by

the value in the pointer.

<dregs> This mode is also used for accesses to the data

RAM, but only the lower 16 addresses in either bank. The

4-bit address comes from the status register and the oper-

and field of the data pointer. Note that data registers are

typically used not for addressing RAM, but loading data

from program memory space.

<memind> This mode is used for indirect accesses to the

program memory. The address of the memory is located in

a RAM location, which is specified by the value in a point-

er. Therefore, @@P1:1 instructs the processor to read

(write is not possible) from a location in memory, which is

specified by a value in RAM, and the location of the RAM

is in turn specified by the value in the pointer. Note that the

data pointer can also be used for a memory access in this

manner, but only one Ò@Ó precedes the pointer. In both

cases, the memory address stored in RAM is incremented

by one, each time the addressing mode is used, to allow

easy transfer of sequential data from program memory.

<accind> Similar to the previous mode, the address for

the program memory read is stored in the Accumulator.

@A in the second operand field loads the number in mem-

ory specified by the address in A.

<direct> The direct mode allows read or write to data

RAM from the Accumulator by specifying the absolute ad-

dress of the RAM in the operand of the instruction. A num-

ber between 0 and 255 indicates a location in RAM0, and

a number between 256 and 511 indicates a location in

RAM1.

<limm> This address mode indicates a long immediate

load. A 16-bit word can be copied directly from the operand

into the specified register or memory.

<simm> This address mode can only be used for imme-

diate transfer of 8-bit data in the operand to the specified

RAM pointer.

CONDITION CODES

The following Instruction Description defines the condition

codes supported by the DSP assembler.

If the instruction description refers to the <cc> (condition

code) symbol in one of its addressing modes, the instruc-

tion will only execute if the condition is true.

Code

Description

Carry

Equal (same as Z)

False

Interrupts Enabled

Minus

No Carry

Not Equal (same as NZ)

NIE

Not Interrupts Enabled

NOV

Not Overßow

NU0

Not User Zero

Code

Description

NU1

Not User One

Not zero

Overßow

Plus (Positive)

User Zero

User One

UGE

Unsigned Greater Than or

Equal (Same as NC)

ULT

Unsigned Less Than (Same as C)

Zero

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