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MOTOROLA
operations that yield single-precision results, then the two register files are completely de-
coupled - thus effectively doubling the amount of registers available for the data ALU.
4.1
CHANGE TO THE PROGRAMMING MODEL (SINGLE PRECISION MODE)
To support the single precision mode, bit 5 of the OMR supports a new single precision
mode (SPM) bit. When OMR bit 5 is clear, the single precision mode is disabled. When
OMR bit 5 is set, the processor is in the single precision mode. The SPM bit is cleared
during reset.
4.2
SINGLE PRECISION MODE DETAILS
The processor supports the following three measures to achieve the Data-ALU Register
File decoupling when it is in single precision mode:
1. Single-precision MOVE operations affect the high and middle portion of the destination
register. They DO NOT clear the low portion of the destination register.
2. Data-ALU floating-point operations that yield single-precision results affect the high
and middle portion of the destination register. They DO NOT clear the low portion of
the destination register.
3. Integer multiply operations (MPYS and MPYU) yield 64-bit results (from the condition
code’s point of view) of which only the 32 least significant bits are written into the low
portion of the destination register. The middle portion of the destination register is not
affected. Thus, the implication is that the largest two integers that can be multiplied in
this mode without a loss of significant digits is 16. If you are using the integer multiply
operation MPYS for the multiplication of 16-bit numbers, you must sign-extend the up-
per 16 bits of the multiplicand and the multiplier to get a valid integer result.
These measures assure that a single-precision floating-point operation or a MOVE does
not overwrite an integer variable stored in the low portion of the destination register. Fur-
thermore these measures assure that an integer multiply does not overwrite a single-pre-
cision floating-point number stored in the high and middle portions of the destination
register. Thereby full decoupling is achieved.
Single Precision Mode does not affect double-precision MOVE operations, long integer
MOVE operations or the single-extended-precision floating-point operations.
31
5
4
3
2
1
0
MA
MB
MC
DE
CE
reserved
Single Precision Mode Bit
SPM
6
Summary of Contents for DSP96002
Page 3: ...1 2 DSP96002 USER S MANUAL MOTOROLA ...
Page 38: ...MOTOROLA DSP96002 USER S MANUAL 3 15 Figure 3 4 Modulo Arithmetic Unit Block Diagram ...
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Page 76: ...MOTOROLA DSP96002 USER S MANUAL 5 23 Figure 5 8 Address Modifier Summary ...
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Page 101: ...MOTOROLA DSP96002 USER S MANUAL 7 15 Figure 7 9 HI Block Diagram One Port ...
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Page 181: ...MOTOROLA DSP96002 USER S MANUAL 10 15 Figure 10 8 Program Address Bus FIFO ...
Page 337: ...MOTOROLA DSP96002 USER S MANUAL A 149 ...
Page 404: ...A 216 DSP96002 USER S MANUAL MOTOROLA PC xxxx D ...
Page 460: ...A 272 DSP96002 USER S MANUAL MOTOROLA SIOP Not affected ...
Page 484: ...A 296 DSP96002 USER S MANUAL MOTOROLA SSH PC SSL SR SP 1 SP ...
Page 519: ...MOTOROLA DSP96002 USER S MANUAL A 331 ...
Page 718: ...MOTOROLA DSP96002 USER S MANUAL B 199 ...
Page 871: ... MOTOROLA INC 1994 MOTOROLA TECHNICAL DATA SEMICONDUCTOR M Addendum ...
Page 888: ...MOTOROLA INDEX 1 INDEX ...
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