mcf5282 Freescale Semiconductor, Inc, mcf5282 Datasheet - Page 51

• Manufacturer Part Number: mcf5282
• Manufacturer: Freescale Semiconductor, Inc

2.2.3
This ColdFire 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
program-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
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 a single stack
pointer (A7), defined for ColdFire ISA_A, is available. EUSP is cleared at reset.
To support dual stack pointers, the following two supervisor instructions are included in the ColdFire
instruction set architecture to load/store the USP:
These instructions are described in the ColdFire Family Programmer’s Reference Manual. All other
instruction references to the stack pointer, explicit or implicit, access the active A7 register.
Freescale Semiconductor
move.l Ay,USP;move to USP
move.l USP,Ax;move from USP
Reset – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –
BDM: Load: 0x088 + n; n = 0–6 (An)
then
else
W
R
Supervisor/User Stack Pointers (A7 and OTHER_A7)
Store: 0x188 + n; n = 0–6 (An)
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9
The SSP is loaded during reset exception processing with the contents of
location 0x0000_0000.
A7 = Supervisor Stack Pointer
OTHER_A7 = User Stack Pointer
A7 = User Stack Pointer
OTHER_A7 = Supervisor Stack Pointer
MCF5282 and MCF5216 ColdFire Microcontroller User’s Manual, Rev. 3
Figure 2-3. Address Registers (A0–A6)
NOTE
Address
8
7
Access: User read/write
6
5
BDM read/write
4
3
2
ColdFire Core
1
0
2-5