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Central Processor Unit (CPU) Registers
4
-10
DSP56303 User’s Manual
example, MOVEC). Parallel move operations affect only the S and L bits of the CCR.
During processor reset, all CCR bits are cleared.
n
The definition of the three 8-bit registers within the SR is primarily for the purpose of
compatibility with other Motorola DSPs. Bit definitions in the following paragraphs
identify the bits within the SR and not within the subregister.
Extended Mode Register (EMR)
Mode Register (MR)
Condition Code Register (CCR)
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
CP[1–0] RM SM CE
SA FV
LF DM SC
S[1–0]
I[1–0]
S
L
E
U
N
Z
V
C
Reset:
1
1
0
0
0
0
0
0
0
0
0
0
0
0
1
1
0
0
0
0
0
0
0
0
Reserved bit. Read as zero; write to zero for future compatibility
Figure 4-1. Status Register (SR)
Table 4-2. Status Register Bit Definitions
Bit Number
Bit Name
Reset Value
Description
23–22
CP[1–0]
11
Core Priority
Under control of the CDP[1–0] bits in the OMR, the CP bits specify the
priority of core accesses to external memory. These bits are compared
against the priority bits of the active DMA channel. If the core priority is
greater than the DMA priority, the DMA waits for a free time slot on the
external bus. If the core priority is less than the DMA priority, the core waits
for a free time slot on the external bus. If the core priority equals the DMA
priority, the core and DMA access the external bus in a round robin pattern
(for example, ... P, X, Y, DMA, P, X, Y, ...).
Priority
Mode
Core
Priority
DMA
Priority
OMR
(CDP[1-0])
SR (CP[1–0])
Dynamic
0
(Lowest)
Determined
by DCRn
(DPR[1–0])
for active
DMA
channel
00
00
1
00
01
2
00
10
3
(Highest)
00
11
Static
core < DMA
01
xx
core = DMA
10
xx
core > DMA
11
xx
21
RM
0
Rounding Mode
Selects the type of rounding performed by the Data ALU during arithmetic
operations. If RM is cleared, convergent rounding is selected. If RM is set,
two’s-complement rounding is selected.
20
SM
0
Arithmetic Saturation Mode
Selects automatic saturation on 48 bits for the results going to the
accumulator. This saturation is performed by a special circuit inside the
MAC unit. The purpose of this bit is to provide an Arithmetic Saturation
mode for algorithms that do not recognize or cannot take advantage of the
extension accumulator.
Содержание DSP56303
Страница 1: ...DSP56303 User s Manual 24 Bit Digital Signal Processor DSP56303UM AD Revision 1 January 2001 ...
Страница 52: ...JTAG OnCE Interface 2 22 DSP56303 User s Manual ...
Страница 114: ...General Purpose Input Output GPIO 5 10 DSP56303 User s Manual ...
Страница 212: ...GPIO Signals and Registers 8 26 DSP56303 User s Manual ...
Страница 268: ...Interrupt Equates A 22 DSP56303 User s Manual ...
Страница 306: ...Programming Sheets B 38 DSP56303 User s Manual ...
Страница 320: ...Index 14 DSP56303 User s Manual ...