SAB80C517-M16 SIEMENS [Siemens Semiconductor Group], SAB80C517-M16 Datasheet - Page 125

• Manufacturer Part Number: SAB80C517-M16
• Description: 8-Bit CMOS Single-Chip Microcontroller
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

7.6
This on-chip arithmetic unit of the SAB 80C517 provides fast 32-bit division, 16-bit multiplication as
well as shift and normalize features. All operations are unsigned integer operations.
The arithmetic unit (further on also called MDU for "Multiplication/Division Unit") has been
integrated to support the 8051 core of the SAB 80C517 in real-time control applications. lt can
increase the execution speed of math-intensive software routines by factor 5 to 10.
The MDU is handled by seven registers, which are memory mapped as special function registers
like any other registers for peripheral control. Therefore, the arithmetic unit allows operations
concurrently to and independent of the CPU’s activity.
The following table describes the four general operations the MDU is able to perform:
Operation
32bit/16bit
16bit/16bit
16bit x 16bit
32-bit normalize
32-bit shift L/R
1) 1
2) The maximal shift speed is 6 shifts per machine cycle
7.6.1
Operating Registers of the MDU
The seven SFR of the MDU consist of registers MD0 to MD5, which contain the operands and the
result (or the remainder, resp.) and one control register called ARCON.
Thus MD0 to MD5 are used twofold:
This means that any calculation of the MDU overwrites its operands. lf a program needs the original
operands for further use, they should be stored in general purpose registers in the internal RAM.
Semiconductor Group
– for the operands before a calculation has been started and
– for storage of the result or remainder after a calculation.
t
CY
= 1 microsecond at 12-MHz oscillator frequency
Arithmetic Unit
Programming the MDU
Result
32bit
16bit
32bit
–
–
Remainder
16bit
16bit
–
–
–
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On-Chip Peripheral Components
Execution Time
6
4
4
6
6
t
t
t
t
t
CY
CY
CY
CY
CY
1)
1)
1)
2)
2)