Z89393 datasheet(13/61 Pages) ZILOG

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Z89323/373/393

16-BIT DIGITAL SIGNAL PROCESSORS

PRELIMINARY

DS95DSP0101 Q4/95

Pn:b are the pointer registers for accessing data RAM, (n

= 0,1,2 refer to the pointer number) (b = 0,1 refers to RAM

Bank 0 or 1). They can be directly read from or written to,

and can point to locations in data RAM or Program Memory.

EXTn are external registers (n = 0 to 7). There are eight 16-

bit registers provided here for mapping external devices

into the address space of the processor. Note that the

actual register RAM does not exist on the chip, but would

exist as part of the internal or external device, such as an

ADC.

BUS is a read-only register which, when accessed, returns

the contents of the D-Bus. Bus is used for emulation only.

Dn:b refers to locations in RAM that can be used as a

pointer to locations in program memory which is efficient

for coefficient addressing. The programmer decides which

location to choose from two bits in the status register and

two bits in the operand. Thus, only the lower 16 possible

locations in RAM can be specified. At any one time, there

are eight usable pointers, four per bank, and the four

pointers are in consecutive locations in RAM. For example,

if S3/S4 = 01 in the status register, then D0:0/D1:0/D2:0/

D3:0 refer to register locations 4/5/6/7 in RAM Bank 0. Note

that when the data pointers are being written to, a number

is actually being loaded to Data RAM, so they can be used

as a limited method for writing to RAM.

SR is the status register (Figure 8) which contains the ALU

status and certain control bits (Table 5).

Table 5. Status Register Bit Functions

Status Register Bit

Function

S15 (N)

ALU Negative

S14 (OV)

ALU Overflow

S13 (Z)

ALU Zero

S12 (L)

Carry

S11 (UI1)

User Input 1

S10 (UI0)

User Input 0

S9 (SH3)

MPY Output Arithmetically

Shifted Right by three bits

S8 (OP)

Overflow Protection

S7 (IE)

Interrupt Enable

S6 (UO1)

User Output 1

S5 (UO0)

User Output 0

S4-S3

“Short Form Direct” bits

S2-S0 (RPL)

RAM Pointer Loop Size

REGISTERS

The internal registers of the Z89323/373/393 are defined

below:

Output of Multiplier, 24-bit

X Multiplier Input, 16-bit

Y Multiplier Input, 16-bit

Accumulator, 24-bit

Status Register, 16-bit

Pn:b

Six Ram Address Pointers, 8-bit each

P C

Program Counter, 16-bit

EXT 0

EXT 1

EXT 2

EXT 3

EXT 4

EXT 5

EXT 6

EXT 7

See Table 6 and Table 7 for the different assignments of

EXT7-EXT0 in the different banks.

EXTn

External Registers, 16-bit

BUS

D-Bus

Dn:b

Eight Data Pointers*

Note:

* These data pointers occupy the first four locations in RAM bank.

P holds the result of multiplications and is read-only.

X and Y are two 16-bit input registers for the multiplier.

These registers can be utilized as temporary registers

when the multiplier is not being used.

A is a 24-bit Accumulator. The output of the ALU is sent to

this register. When 16-bit data is transferred into this

significant eight bits are set to zero. Only the upper 16 bits

are transferred to the destination register when the

Accumulator is selected as a source register in transfer

instructions.

Z89393 Datasheet(PDF) 13 Page - Zilog, Inc.

Z89393 Datasheet(HTML) 13 Page - Zilog, Inc.

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