Address Attribute Registers (Aar[0-3]) - Freescale Semiconductor DSP56311 User Manual

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
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.
23 22 21
BAC11 BAC10 BAC9
11 10 9
BNC3 BNC2 BNC1
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 Reset
Bit Name
Number Value
23–12 BAC[11–0]
11–8 BNC[3–0]
Freescale Semiconductor
pins. The associated
20 19
BAC8 BAC7 BAC6
8 7
BNC0 BPAC
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.
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
/ pin is asserted if the address defined by
AAn RASn
18 17 16
BAC5 BAC4
6 5 4
BYEN BXEN
Description
Bus Interface Unit (BIU) Registers
15 14 13
BAC3 BAC2 BAC1
3 2 1
BPEN BAAP BAT1
12
BAC0
0
BAT0
4-25