DSP56311EVM【PDF 99/360 页】KIT EVALUATION FOR DSP56311

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Bus Interface Unit (BIU) Registers

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 DSP56311 does not support address multiplexing.

BAC11

BNC3

BAC10

BNC2

BAC9

BNC1

BAC8

BNC0

BAC7

BPAC

BAC6

BAC5

BYEN

BAC4

BXEN

BAC3

BPEN

BAC2

BAAP

BAC1

BAT1

BAC0

BAT0

Reserved bit. Read as zero; write to zero for future compatibility

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

23–12

Bit Name

BAC[11–0]

Reset

Value

Bus Address to Compare

Description

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[3–0]

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.

DSP56311 User’s Manual, Rev. 2

Freescale Semiconductor

4-25

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