dsp56800e Freescale Semiconductor, Inc, dsp56800e Datasheet - Page 246

• Manufacturer Part Number: dsp56800e
• Description: 16-bit Digital Signal Controller Core
• Manufacturer: Freescale Semiconductor, Inc

Program Controller
SR
Bits in the CCR portion of the status register are affected by data ALU operations, AGU arithmetic
instructions, bit-manipulation instructions, and so forth. Bits in the MR are affected by processor reset,
exception processing, flow control instructions, and many others. During processor reset, all CCR bits are
cleared, the interrupt mask bits in the MR are both set, and the LF bit is cleared. The program extension bit
values depend on the value of the reset vector.
8-8
RESET
LF
Bit 15
P4–P0
Bits 14–10
I1–I0
Bits 9–8
SZ
Bit 7
L
Bit 6
E
Bit 5
U
Bit 4
N
Bit 3
Z
Bit 2
V
Bit 1
C
Bit 0
TYPE
Name
BIT 15
LF
rw
0
Loop Flag—Indicates whether a program loop is
active or whether HWS has been written to at
least once without being read
Program Counter Extension—Bits 20–16 of
the program counter
Interrupt Mask—Masks or enables the four
interrupt levels
Size—Indicates growth beyond a certain point in
the size of an accumulator value
Limit—Indicates whether data limiting has been
performed since this bit was last cleared
Extension in Use—Indicates whether an accu-
mulator extension register is in use
Unnormalized—Shows whether a result value
is normalized or not
Negative—Indicates whether result of last oper-
ation was negative or positive
Zero—Indicates whether result of last operation
was zero or not
Overflow—Indicates whether result of last oper-
ation overflowed its destination
Carry—Set if a carry out or borrow was gener-
ated in addition or subtraction
P4
14
0
r
P3
13
0
r
P2
12
0
r
Description
P1
11
DSP56800E Core Reference Manual
0
r
Table 8-2. SR Bit Descriptions
10
P0
0
r
Status Register
rw
I1
9
1
rw
I0
8
1
SZ
rw
7
0
0 = No DO loop active.
1 = DO loop active.
Note: See Section 8.4, “Hardware Stack.”
Dependent on execution.
00 = Allow all interrupts.
01 = Mask level 0.
10 = Mask levels 0 and 1.
11 = Mask levels 0, 1, and 2.
0 = Accumulator value is small.
1 = Accumulator value is large.
0 = No limiting performed.
1 = Limiting has been performed.
0 = Extension not in use.
1 = Extension in use.
0 = Normalized.
1 = Not normalized.
0 = Result was positive.
1 = Result was negative.
0 = Result was non-zero.
1 = Result was zero.
0 = Result did not overflow.
1 = Result overflowed destination.
0 = No carry occurred during operation.
1 = Carry out occurred during operation.
rw
6
L
0
rw
E
5
0
rw
U
4
0
Settings
Freescale Semiconductor
rw
N
3
0
rw
2
Z
0
rw
V
1
0
BIT 0
rw
C
0