DSP56303 datasheet(84/292 Pages) FREESCALE

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DSP56303 User’s Manual, Rev. 2

4-26

Freescale Semiconductor

Core Configuration

4.6.3 Address Attribute Registers (AAR[0–3])

The Address Attribute Registers (AAR[0–3]) are read/write registers that control the activity of

the AA0/RAS0–AA3/RAS3 pins. The associated AAn/RASn pin is asserted if the address defined by

the BAC bits in the associated AAR matches the exact number of external address bits defined by

the BNC bits, and the external address space (X data, Y data, or program) is enabled by the AAR.

Figure 4-8 shows an AAR register; Table 4-10 lists the bit definitions.

Note:

The DSP56303 does not support address multiplexing.

Figure 4-8. Address Attribute Registers (AAR[0–3]) (X:$FFFFF9–$FFFFF6)

Table 4-10. Address Attribute Registers (AAR[0–3]) Bit Definitions

Bit

Number

Bit Name

Reset

Value

Description

23–12

BAC

Bus Address to Compare

Read/write control bits that define the upper 12 bits of the 24-bit address with which to

compare the external address to determine whether to assert the corresponding AA/RAS

signal. This is also true of 16-bit compatibility mode. The BNC[3–0] bits define the number of

address bits to compare.

11–8

BNC

Bus Number of Address Bits to Compare

Specify the number of bits (from the BAC bits) that are compared to the external address.

The BAC bits are always compared with the Most Significant Portion of the external address

(for example, if BNC[3–0] = 0011, then the BAC[11–9] bits are compared to the 3 MSBs of

the external address). If no bits are specified (that is, BNC[3–0] = 0000), the AA signal is

activated for the entire 16 M-word space identified by the space enable bits (BPEN, BXEN,

BYEN), but only when the address is external to the internal memory map. The

combinations BNC[3–0] = 1111, 1110, 1101 are reserved.

BAC0

BPEN

BYEN

BAT1

BAAP

BXEN

BAC8

BAT0

BAC3 BAC2

BAC11

BAC5

BAC7 BAC6

BAC9

BAC10

BAC1

BNC3

BNC1

BNC2

BNC0

BAC4

BPAC

Reserved Bit. Write to zero for future compatibility.

External Access Type

AA pin polarity

Program space Enable

X data space Enable

Y data space Enable

Reserved

Packing Enable

Number of Address bit to

compare

Address to Compare

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