SAB80C517-M16 SIEMENS [Siemens Semiconductor Group], SAB80C517-M16 Datasheet - Page 126

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

On-Chip Peripheral Components
Operation of the MDU
The MDU can be regarded as a special coprocessor for multiplication, division and shift. Its
operations can be divided into three phases (see also figure 7-55):
1) Loading the MDx registers
2) Executing the calculation
3) Reading the result from the MDx registers
During phase two, the MDU works on its own parallelly to the CPU. Execution times of the above
table refer to this phase. Because of the fast operation and the determined execution time for SAB
80C517’s instructions, there is no need for a busy flag. The CPU may execute a determined number
of instructions before the result is fetched. The result and the remainder of an operation may also
be stored in the MDx registers for later use.
Phase one and phase three require CPU activity. In these phases the CPU has to transfer the
operands and fetch the results.
Figure 7-55
Operating Phases of the MDU
Semiconductor Group
127