dsp56000 Freescale Semiconductor, Inc, dsp56000 Datasheet - Page 84

• Manufacturer Part Number: dsp56000
• Description: 24-bit Digital Signal Processor Family Manual
• Manufacturer: Freescale Semiconductor, Inc

ation, move the contents in accumulator A into the location in Y data memory pointed to
by R4 and postdecrement R4. The third instruction, I3, is the same as I1, except the
rounding operation is not performed.
5.4
The program control unit features LA and LC registers which support the DO loop instruc-
tion and the standard program flow-control resources, such as a PC, complete SR, and
SS. With the exception of the PC, all registers are read/write to facilitate system debug-
ging. Figure 5-4 shows the program control unit programming model with the six registers
and SS. The following paragraphs give a detailed description of each register.
5.4.1 Program Counter
This 16-bit register contains the address of the next location to be fetched from program
memory space. The PC can point to instructions, data operands, or addresses of oper-
ands. References to this register are always inherent and are implied by most instructions.
5 - 8
PROGRAMMING MODEL
23 16 15
23 16 15
31
*
*
LOOP ADDRESS
REGISTER (LA)
COUNTER (PC)
PROGRAM
Figure 5-4 Program Control Unit Programming Model
SSH
SYSTEM STACK
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16 15
0
0
23 16 15
23 16 15
LOOP COUNTER (LC)
*
*
PROGRAM CONTROL UNIT
REGISTER (SR)
PROGRAMMING MODEL
MR
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STATUS
SSL
PROGRAM CONTROL UNIT
8 7
CCR
0
0
0
15
1
*
WITH ZERO FOR FUTURE COMPATIBILITY
READ AS ZERO, SHOULD BE WRITTEN
23
OPERATING MODE REGISTER (OMR)
23
*
*
6 5
STACK POINTER (SP)
8 7
*
SD
6
*
5
MC
4
YD
3
MOTOROLA
DE MB
2
1
MA
0
0