![Intel 80C196NU Скачать руководство пользователя страница 54](http://html1.mh-extra.com/html/intel/80c196nu/80c196nu_user-manual_2072209054.webp)
3-5
ADVANCED MATH FEATURES
3.4
ACCUMULATOR CONTROL AND STATUS REGISTER (ACC_STAT)
The ACC_STAT register controls the operating mode and reflects the status of the accumulator.
The mode bits (FME and SME) are effective only for signed multiplication. Table 3-2 describes
the 80C196NU’s operation with each of the four possible configurations of these bits.
ACC_STAT
(80C196NU)
Address:
Reset State:
0BH
00H
The accumulator control and status (ACC_STAT) register enables and disables fractional and
saturation modes and contains three status flags that indicate the status of the accumulator’s
contents.
7
0
80C196NU
FME
SME
—
—
—
STOVF
OVF
STSAT
Bit
Number
Bit
Mnemonic
Function
7
FME
Fractional Mode Enable
Set this bit to enable fractional mode. (See Table 3-2.) In this mode, the
result of a signed multiplication instruction is shifted left by one bit before it
is added to the contents of the accumulator.
For unsigned multiplication, this bit is ignored.
6
SME
Saturation Mode Enable
Set this bit to enable saturation mode. (See Table 3-2.) In this mode, the
result of a signed multiplication operation is not allowed to overflow or
underflow.
For unsigned multiplication, this bit is ignored.
5:3
—
Reserved; for compatibility with future devices, write zeros to these bits.
2
STOVF
Sticky Overflow Flag
For unsigned multiplication, this bit is set if a carry out of bit 31 occurs.
Unless saturation mode is enabled, this bit is set for signed multiplication to
indicate that the sign bit of the accumulator and the sign bit of the addend
are equal, but the sign bit of the result is the opposite. (See Table 3-2.)
Software can clear this flag; hardware does not clear it.
1
OVF
Overflow Flag
This bit indicates that an overflow occurred during the preceding accumu-
lation. (See Table 3-2.)
This flag is dynamic; it can change after each accumulation.
0
STSAT
Sticky Saturation Flag
This bit indicates that a saturation has occurred during accumulation with
saturation mode enabled. (See Table 3-2.)
Software can clear this flag; hardware does not clear it.
Figure 3-2. Accumulator Control and Status (ACC_STAT) Register
Содержание 80C196NU
Страница 1: ...8XC196NP 80C196NU Microcontroller User s Manual...
Страница 2: ...8XC196NP 80C196NU Microcontroller User s Manual August 1995 Order Number 272479 002...
Страница 18: ...1 Guide to This Manual...
Страница 19: ......
Страница 31: ......
Страница 32: ...2 Architectural Overview...
Страница 33: ......
Страница 48: ...3 Advanced Math Features...
Страница 49: ......
Страница 56: ...4 Programming Considerations...
Страница 57: ......
Страница 72: ...5 Memory Partitions...
Страница 73: ......
Страница 106: ...6 Standard and PTS Interrupts...
Страница 107: ......
Страница 144: ...7 I O Ports...
Страница 145: ......
Страница 165: ......
Страница 166: ...8 Serial I O SIO Port...
Страница 167: ......
Страница 183: ......
Страница 184: ...9 Pulse width Modulator...
Страница 185: ......
Страница 196: ...10 Event Processor Array EPA...
Страница 197: ......
Страница 225: ......
Страница 226: ...11 Minimum Hardware Considerations...
Страница 227: ......
Страница 239: ......
Страница 240: ...12 Special Operating Modes...
Страница 241: ......
Страница 255: ......
Страница 256: ...13 Interfacing with External Memory...
Страница 257: ......
Страница 303: ......
Страница 304: ...A Instruction Set Reference...
Страница 305: ......
Страница 373: ......
Страница 374: ...B Signal Descriptions...
Страница 375: ......
Страница 390: ...C Registers...
Страница 391: ......
Страница 447: ......
Страница 448: ...Glossary...
Страница 449: ......
Страница 458: ...Index...
Страница 459: ......