DSP56156ROM datasheet(11/76 Pages) MOTOROLA

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Pin Descriptions

MOTOROLA

DSP56156 Data Sheet

trigger input is used for noise immunity.

When the reset pin is deasserted, the ini-

tial chip operating mode is latched from

the MODA and MODB pins, and the ini-

tial bus operating mode is latched from

the MODC pin. The internal reset signal

should be deasserted synchronized with

the internal clocks.

Host Interface

H0-H7 (Host Data Bus)

— bidirectional. This

bidirectional data bus is used to transfer

data between the host processor and the

DSP. This bus is an input unless enabled

by a host processor read. H0-H7 may be

programmed as Port B general purpose

parallel I/O pins called PB0-PB7 when

the Host Interface (HI) is not being used.

HA0-HA2 (Host Address 0-2)

— input*. These

inputs provide the address selection

for each HI register and are stable

when HEN is asserted. HA0-HA2 may

be programmed as Port B general pur-

pose parallel I/O pins called PB8-PB10

when the HI is not being used.

HR/W (Host Read/Write)

— input*. This in-

put selects the direction of data transfer

for each host processor access. If HR/W

is high and HEN is asserted, H0-H7 are

outputs and DSP data is transferred to

the host processor. If HR/W is low and

HEN is asserted, H0-H7 are inputs and

host data is transferred to the DSP.

When HEN is asserted, HR/W is stable.

HR/W may be programmed as a gen-

eral purpose I/O pin called PB11

when the HI is not being used.

HEN (Host Enable)

— input*. This input en-

ables a data transfer on the host data

bus. When HEN is asserted and HR/W

is high, H0-H7 becomes an output and

DSP data may be latched by the host

processor. When HEN is asserted and

HR/W is low, H0-H7 is an input and

host data is latched inside the DSP

when HEN is deasserted. Normally a

chip select signal derived from host ad-

dress decoding and an enable clock is

connected to the Host Enable. HEN

may be programmed as a general pur-

pose I/O pin called PB12 when the HI

is not being used.

HREQ (Host Request)

— output*. This open-

drain output signal is used by the HI to

request service from the host proces-

sor. HREQ may be connected to an in-

terrupt request pin of a host processor,

a transfer request of a DMA controller,

or a control input of external circuitry.

HREQ is asserted when an enabled re-

quest occurs in the HI. HREQ is deas-

serted when the enabled request is

cleared or masked, DMA HACK is as-

serted, or the DSP is reset. HREQ may

be programmed as a general purpose

I/O pin (not open-drain) called PB13

when the HI is not being used.

HACK (Host Acknowledge)

— input*. This

input has two functions:

• to provide a host acknowledge signal

for DMA transfers and,

• to control handshaking and to pro-

vide a host interrupt acknowledge

compatible with MC68000 family

processors.

If programmed as a host acknowledge

signal, HACK may be used as a data

strobe for HI DMA data transfers. If pro-

grammed as an MC68000 host interrupt

Host Interface

* These pins can be bidirectional when programmed as general purpose I/O.

Interrupt and Mode Control

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

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