MOTOROLA
Chapter 2. ColdFire Core
2-7
Processor Register Description
2.2.3.2
Supervisor/User Stack Pointers (A7 and OTHER_A7)
The MCF5282 architecture supports two independent stack pointer (A7) registers
—
the
supervisor stack pointer (SSP) and the user stack pointer (USP). The hardware
implementation of these two programmable-visible 32-bit registers does not identify one as
the SSP and the other as the USP. Instead, the hardware uses one 32-bit register as the active
A7 and the other as OTHER_A7. Thus, the register contents are a function of the processor
operation mode, as shown in the following:
if SR[S] = 1
then
A7 = Supervisor Stack Pointer
OTHER_A7 = User Stack Pointer
else
A7 = User Stack Pointer
OTHER_A7 = Supervisor Stack Pointer
The BDM programming model supports direct reads and writes to A7 and OTHER_A7. It
is the responsibility of the external development system to determine, based on the setting
of SR[S], the mapping of A7 and OTHER_A7 to the two program-visible definitions (SSP
and USP). This functionality is enabled by setting the enable user stack pointer bit,
CACR[EUSP]. If this bit is cleared, only the stack pointer (A7), defined for previous
ColdFire versions, is available. EUSP is zero at reset.
If EUSP is set, the appropriate stack pointer register (SSP or USP) is accessed as a function
of the processor’s operating mode. To support dual stack pointers, the following two
privileged M68000 instructions are added to the ColdFire instruction set architecture to
load/store the USP :
move.l Ay, USP; move to USP
move.l USP, Ax; move from USP
These instructions are described in the
ColdFire Family Programmer’s Reference Manual
.
12
M
Master/interrupt state. This bit is cleared by an interrupt exception, and
can be set by software during execution of the RTE or move to SR
instructions.
11
—
Reserved, should be cleared.
10–8
I
Interrupt level mask. Defines the current interrupt level. Interrupt
requests are inhibited for all priority levels less than or equal to the
current level, except the edge-sensitive level 7 request, which cannot
be masked.
7–5
—
Reserved, should be cleared.
4–0
CCR
Refer to Table 2-1.
Table 2-2. SR Field Descriptions (continued)
Bits
Name
Description
Summary of Contents for ColdFire MCF5281
Page 124: ...3 20 MCF5282 User s Manual MOTOROLA EMAC Instruction Set Summary ...
Page 141: ...MOTOROLA Chapter 5 Static RAM SRAM 5 5 SRAM Programming Model ...
Page 142: ...5 6 MCF5282 User s Manual MOTOROLA SRAM Programming Model ...
Page 168: ...6 26 MCF5282 User s Manual MOTOROLA Interrupts ...
Page 186: ...7 18 MCF5282 User s Manual MOTOROLA Functional Description ...
Page 228: ...9 22 MCF5282 User s Manual MOTOROLA Functional Description ...
Page 246: ...10 18 MCF5282 User s Manual MOTOROLA Low Power Wakeup Operation ...
Page 254: ...11 8 MCF5282 User s Manual MOTOROLA Memory Map and Registers ...
Page 264: ...12 10 MCF5282 User s Manual MOTOROLA Chip Select Registers ...
Page 280: ...13 16 MCF5282 User s Manual MOTOROLA Misaligned Operands ...
Page 314: ...14 34 MCF5282 User s Manual MOTOROLA MCF5282 External Signals ...
Page 339: ...MOTOROLA Chapter 15 Synchronous DRAM Controller Module 15 25 SDRAM Example ...
Page 340: ...15 26 MCF5282 User s Manual MOTOROLA SDRAM Example ...
Page 356: ...16 16 MCF5282 User s Manual MOTOROLA DMA Controller Module Functional Description ...
Page 408: ...17 52 MCF5282 User s Manual MOTOROLA Buffer Descriptors ...
Page 446: ...20 24 MCF5282 User s Manual MOTOROLA Interrupts ...
Page 474: ...22 18 MCF5282 User s Manual MOTOROLA Programming Model ...
Page 510: ...23 36 MCF5282 User s Manual MOTOROLA Operation ...
Page 526: ...24 16 MCF5282 User s Manual MOTOROLA I2C Programming Examples ...
Page 672: ...28 12 MCF5282 User s Manual MOTOROLA Functional Description ...
Page 718: ...29 46 MCF5282 User s Manual MOTOROLA Motorola Recommended BDM Pinout ...
Page 750: ...32 8 MCF5282 User s Manual MOTOROLA Ordering Information ...