DSP56362AD datasheet(16/168 Pages) MOTOROLA

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1-8

DSP56362 Advance Information

MOTOROLA

Signal/Connection Descriptions

External Memory Expansion Port (Port A)

Output

(deasserted)

Bus Request—BR is an active-low output, never tri-

stated. BR is asserted when the DSP requests bus

mastership. BR is deasserted when the DSP no longer

needs the bus. BR may be asserted or deasserted

independent of whether the DSP56362 is a bus master

or a bus slave. Bus “parking” allows BR to be deasserted

even though the DSP56362 is the bus master. (See the

description of bus “parking” in the BB signal description.)

The bus request hold (BRH) bit in the BCR allows BR to

be asserted under software control even though the DSP

does not need the bus. BR is typically sent to an external

bus arbitrator that controls the priority, parking, and

tenure of each master on the same external bus. BR is

only affected by DSP requests for the external bus, never

for the internal bus. During hardware reset, BR is

deasserted and the arbitration is reset to the bus slave

state.

Input

Ignored Input

Bus Grant—BG is an active-low input. BG is asserted by

an external bus arbitration circuit when the DSP56362

becomes the next bus master. When BG is asserted, the

DSP56362 must wait until BB is deasserted before taking

bus mastership. When BG is deasserted, bus mastership

is typically given up at the end of the current bus cycle.

This may occur in the middle of an instruction that

requires more than one external bus cycle for execution.

The default mode of operation of this signal requires a

setup and hold time referred to CLKOUT. But CLKOUT

operation is not guaranteed from 100MHz and up, so the

asynchronous bus arbitration must be used for clock

frequencies 100MHz and above. The asynchronous bus

arbitration is enabled by setting the ABE bit in the OMR

Table 1-7 External Bus Control Signals (Continued)

Signal

Name

Type

State during

Reset

Signal Description

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

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