Motorola DSP56301 user manual Address Attribute Registers AAR0-3, Bus Address to Compare

Bus Interface Unit (BIU) Registers

4.6.3Address 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 4-8shows an AAR register; Table 4-11lists the bit definitions.

Note: The DSP56301 does not support address multiplexing.

23	22	21	20		19		18	17	16	15	14	13		12
BAC11	BAC10	BAC9		BAC8		BAC7	BAC6	BAC5	BAC4	BAC3	BAC2	BAC1		BAC0
															Address to Compare
11	10	9	8		7		6	5	4	3	2	1		0
BNC3	BNC2	BNC1	BNC0			BPAC		BYEN	BXEN	BPEN	BAAP	BAT1	BAT0
															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

Reserved Bit. Write to zero for future compatibility.

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

Table 4-11.Address Attribute Registers (AAR[0–3]) Bit Definitions

Bit	Bit Name	Reset	Description
Number		Value
23–12	BAC[11–0]	0	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[3–0]	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.

Core Configuration 4-27