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Local Memory
MCF5272 ColdFire
®
Integrated Microprocessor User’s Manual, Rev. 3
Freescale Semiconductor
4-3
4.3.2.1
SRAM Base Address Register (RAMBAR)
RAMBAR determines the base address location of the internal SRAM module, as well as the definition of
the types of accesses allowed for it.
•
RAMBAR is a 32-bit write-only supervisor control register. It is accessed in the CPU address space
via the MOVEC instruction with an Rc encoding of 0xC04. RAMBAR can be read or written in
background debug mode (BDM). At system reset, the V bit is cleared and the remaining bits are
uninitialized. To access the SRAM module, RAMBAR must be written with the appropriate base
address after system reset.
•
The SRAM base address register (RAMBAR) can be accessed only in supervisor mode using the
MOVEC instruction with an Rc value of 0xC04.
Figure 4-1. SRAM Base Address Register (RAMBAR)
RAMBAR fields are described in
.
31
12 11
9
8
7
6
5
4
3
2
1
0
Field
BA
—
WP
—
C/I SC SD UC UD V
Reset
—
0
R/W
W for CPU; R/W for debug
Address
CPU space + 0xC04
Table 4-2. RAMBAR Field Description
Bits
Name
Description
31–12
BA
Base address. SRAM module base address. The SRAM module occupies a 4-Kbyte space defined
by BA. SRAM can reside on any 4-Kbyte boundary in the 4-Gbyte address space.
11–9
—
Reserved, should be cleared.
8
WP
Write protect. Controls read/write properties of the SRAM.
0 Allows read and write accesses to the SRAM module.
1 Allows only read accesses to the SRAM module. Any attempted write reference generates an
access error exception to the ColdFire processor core.
7–6
—
Reserved, should be cleared.
5–1
C/I,
SC,
SD,
UC, UD
Address space masks (AS
n
). These fields allow certain types of accesses to be masked, or inhibited
from accessing the SRAM module. These bits are useful for power management as described in
Section 4.3.2.3, “Programming RAMBAR for Power Management
.” In particular, C/I is typically set.
The address space mask bits are follows:
C/I = CPU space/interrupt acknowledge cycle mask. Note that C/I must be set if BA = 0.
SC = Supervisor code address space mask
SD = Supervisor data address space mask
UC = User code address space mask
UD = User data address space mask
For each AS
n
bit:
0 An access to the SRAM module can occur for this address space
1 Disable this address space from the SRAM module. References to this address space cannot
access the SRAM module and are processed like other non-SRAM references.
0
V
Valid. Enables/disables the SRAM module. V is cleared at reset.
0 RAMBAR contents are not valid.
1 RAMBAR contents are valid.
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