Texas Instruments TMS320C3x 사용자 설명서
Programmable Bank Switching
10-17
TMS320C32 Enhanced External Memory Interface
10.5 Programmable Bank Switching
Programmable bank switching allows you to switch between external memory
banks without having to insert wait states externally due to memories that require
several cycles to turn off. Bank switching is implemented on STRB0 and STRB1
only.
banks without having to insert wait states externally due to memories that require
several cycles to turn off. Bank switching is implemented on STRB0 and STRB1
only.
The size of a bank is determined by the number of bits specified to be examined
on the BNKCMP field of the primary bus control register. For example, if
BNKCMP = 16, the 16 MSBs of the address are used to define a bank (see
Figure 9–4). Since addresses are 24 bits, the bank size is specified by the eight
LSBs, yielding a bank size of 256 words. If BNKCMP
on the BNKCMP field of the primary bus control register. For example, if
BNKCMP = 16, the 16 MSBs of the address are used to define a bank (see
Figure 9–4). Since addresses are 24 bits, the bank size is specified by the eight
LSBs, yielding a bank size of 256 words. If BNKCMP
≥
16, only the 16 MSBs
are compared. Bank sizes from 2
8
= 256 to 2
24
= 16M are allowed. Table 9–6
summarizes the relationship between BNKCMP, the address bits used to define
a bank, and the resulting bank size.
a bank, and the resulting bank size.
Figure 10–8. BNKCMP Example
23
8
7
0
24-bit address
Number of bits to compare
Defines bank size
Table 10–4. BNKCMP and Bank Size
BNKCMP
MSBs Defining a Bank
Bank Size (32-Bit Words)
00000
None
224 = 16M
00001
23
223 = 8M
00010
23–22
222 = 4M
00011
23–21
221 = 2M
00100
23–20
220 = 1M
00101
23–19
219 = 512K
00110
23–18
218 = 256K
00111
23–17
217 = 128K
01000
23–16
216 = 64K
01001
23–15
215 = 32K
01010
23–14
214 = 16K
01011
23–13
213 = 8K
01100
23–12
212 = 4K
01101
23–11
211 = 2K
01110
23–10
210 = 1K
01111
23–9
29 = 512
10000
23–8
28
= 256
10001–11111
Reserved
Undefined