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FlexBus
Field
31–16
Base address mask. Defines the chip-select block size by masking address bits. Setting a BAM bit causes the
BAM
corresponding CSAR bit to be a don't care in the decode.
0 Corresponding address bit is used in chip-select decode.
1 Corresponding address bit is a don't care in chip-select decode.
The block size for FB_CSn is 2
For example, if CSAR0 equals 0x0000 and CSMR0[BAM] equals 0x0008, FB_CS0 addresses two discontinuous
64-Kbyte memory blocks: one from 0x0_0000–0x0_FFFF and one from 0x8_0000–0x8_FFFF.
Likewise, for FB_CS0 to access 32 Mbytes of address space starting at location 0x0, FB_CS1 must begin at the next
byte after FB_CS0 for a 16-Mbyte address space. Then, CSAR0 equals 0x0000, CSMR0[BAM] equals 0x01FF,
CSAR1 equals 0x0200, and CSMR1[BAM] equals 0x00FF.
15–9
Reserved, must be cleared.
8
Write protect. Controls write accesses to the address range in the corresponding CSAR. Attempting to write to the
WP
range of addresses for which CSARn[WP] is set results in the appropriate chip-select not being selected, as well as
a bus error sent to the interrupt controller.
0 Read and write accesses are allowed
1 Only read accesses are allowed
7–1
Reserved, must be cleared.
0
Valid bit. Indicates whether the corresponding CSAR, CSMR, and CSCR contents are valid. Programmed
V
chip-selects do not assert until V bit is set (except for FB_CS0, which acts as the global chip-select). Reset clears
each CSMRn[V]. At reset, no chip-select other than FB_CS0 can be used until the CSMR0[V] is set. At which point
FB_CS[5:0] functions as configured.
0 Chip-select invalid
1 Chip-select valid
18.3.3
Chip-Select Control Registers (CSCR0–CSCR5)
Each CSCRn,
Figure
18-3, controls the auto-acknowledge, address setup and hold times, port size, burst
capability, and activation of each chip-select. To support the global chip-select, FB_CS0, the CSCR0 reset
18-6
Table 18-4. CSMRn Field Descriptions
Description
n
; n = (number of bits set in respective CSMR[BAM]) + 16.
MCF52277 Reference Manual, Rev. 1
Freescale Semiconductor
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