Analog Devices ADSP-BF53x Blackfin Reference page 208

can be used for 8-, 16-, and 32-bit memory accesses. For added
mode protection,
is accessible in User mode.
USP
Do not assume the L-registers are automatically initialized to zero
for linear addressing. The I-, M-, L-, and B-registers contain ran-
dom values after reset. For each I-register used, programs must
initialize the corresponding L-registers to zero for linear addressing
or to the buffer length for circular buffer addressing.
Note all data address registers must be initialized individually. Ini-
tializing a B-register does not automatically initialize the I-register.
Data Address Registers
Figure 5-2. Address Arithmetic Unit
5-4 ADSP-BF53x/BF56x Blackfin Processor Programming Reference
is accessible only in Supervisor mode, while
SP
Address Arithmetic Unit Registers
I0 L0 B0
I1 L1 B1
I2 L2 B2
I3 L3 B3
Supervisor only register. Attempted read or
write in User mode causes an exception error.
Pointer
Registers
M0 P0
M1
P1
M2
P2
M3
P3
P4
P5
User SP
Supervisor SP
FP