
10-8
MCF5249UM
MOTOROLA
Programming Model
10.4.2.3 CHIP SELECT CONTROL REGISTER
CSCR0 to CSCR3 control the auto acknowledge, external master support, port size, burst capability, and
activation of each of the chip selects.
For CSCR0, bits BSTR, and BSTW are initialized to 0 by reset; bits WS[3:0] and BEM are initialized to 1 by
reset; while AA, PS1, and PS0 are loaded with “110”, respectively at reset. For CSCR1 to CSCR3 none of
WP, AM, C/I, SC,
SD, UC, UD
These fields mask specific address spaces, placing the chip select in a specific
address space or spaces. If an address space mask bit were cleared, an access to
a location in that address space can activate the corresponding chip select. If an
address space mask bit were set, an access to a location in that address space
becomes a regular external bus access, and no chip select is activated.
AM: alternate master access (DMA)
C/I: interrupt cycle access
SC: Supervisor code access
SD: supervisor data access
UC: user code access
UD: user data access
For each address space mask bit (AM, C/I, SC, SD, UC, UD):
0 = Do not mask this address space for the chip select. An access using the chip
select can occur for this address space.
1 = Mask this address space from the chip select activation. If this address space is
accessed, no chip select activation occurs on the external cycle.
WP
The Write Protect bit can restrict write accesses to the address range in a CSAR.
An attempt to write to the range of addresses specified in a CSAR that has this bit
set results in the appropriate chip select not being selected. No exception occurs.
0 = Both read and write accesses are allowed.
1 = Only read access is allowed.
AM
The Alternate Master bit indicates if alternate master (DMA) access is allowed or
denied
0 = Alternate master access is allowed
1 = Alternate master access is denied
V
The Valid bit indicates that the contents of its address register, mask register, and
control register are valid. The programmed chip selects do not assert until the V-bit
is set (except for CS0 which acts as the global (boot) chip select–see
A reset clears the V-bit in each CSMR.
0 = Chip select invalid
1 = Chip select valid
Table 10-6 Chip Select Mask Bit Descriptions (Continued)
BIT NAME
DESCRIPTION
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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