APR2SLASHD datasheet(11/101 Pages) NXP

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DSP56001A

Bus Control

MOTOROLA

DSP56001A/D, Rev. 1

1-5

BUS CONTROL

Table 1-7

Bus Control Signals

Signal

Name

Signal

Type

State

during

Reset

Signal Description

Output Tri-stated Program Memory Select—PS is asserted low for external program

memory access. PS is tri-stated when the BG or RESET signal is asserted.

Output Tri-stated Data Memory Select—DS is asserted low for external data memory

access. DS is tri-stated when the BG or RESET signal is asserted.

X/Y

Output Tri-stated X/Y External Memory Select—This output is driven low during external

Y data memory accesses. It is also driven low during external exception

vector fetches when operating in the Development mode. X/Y is tri-stated

when the BG or RESET signal is asserted.

Input/

Output

Tri-stated Bus Request/Wait—The bus request input BR allows another device such

as a processor or DMA controller to become master of the external data

bus D0–D23 and external address bus a0–a15. When operating mode

always release the external data bus D0–D23, address bus A0–A15, and

bus control signals PS, DS, X/Y, RD, and WR (i.e. Port A), by tri-stating

these pins after execution of the current instruction has been completed.

If OMR bit 7 is set, this pin is an input that allows an external device to

force wait states during an external Port A operation for as long as WT is

asserted.

Note:

To prevent erroneous operation, pull up the BR/WT signal when

it is not in use.

Input/

Output

Tri-stated Bus Grant/Bus Select—If OMR Bit 7 is clear, this output is asserted to

acknowledge an external bus request after Port A has been released.

If OMR Bit 7 is set, this signal is bus strobe, and is asserted when the DSP

accesses Port A.

Output Tri-stated Write Enable—WR is asserted during external memory write cycles. WR

is tri-stated when the BG or RESET signal is asserted.

Output Tri-stated Read Enable—RD is asserted during external memory read cycles. RD is

tri-stated when the BG or RESET signal is asserted.

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

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