SAB80C517-M16 SIEMENS [Siemens Semiconductor Group], SAB80C517-M16 Datasheet - Page 127

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

How to Select an Operation
The MDU has no dedicated instruction register (only for shift and normalize operations, register
ARCON is used in such a way). The type of calculation the MDU has to perform is selected following
the order in which the MDx registers are written to (see table 7-11). This mechanism also reduces
execution time spent for controlling the MDU. Hence, a special write sequence selects an operation.
The MDU monitors the whole write and read-out sequence to ensure that the CPU has fetched the
result correctly and was not interrupted by another calculation task. (See section 7.6.4 "The Error
Flag").
Thus, a complete operation lasts from writing the first byte of the operand in phase 1 until reading
the last byte of the result in phase 3.
7.6.2
The general mechanism to start an MDU activity has been described above. The following
description of the write and read sequences adds to the information given in the table below where
the write and read operations necessary for a multiplication or division are listed.
Table 7-11
Programming the MDU for Multiplication and Division
Operation
First Write
Last Write
First Read
Last Read
Semiconductor Group
Multiplication/Division
MD0
MD1
MD2
MD3
MD4
MD5
MD0
MD1
MD2
MD3
MD4
MD5
32Bit/16Bit
D’endL
D’end
D’end
D’endH
D’orL
D’orH
QuoL
Quo
Quo
QuoH
RemL
RemH
128
MD0
MD1
MD4
MD5
MD0
MD1
MD4
MD5
16Bit/16Bit
On-Chip Peripheral Components
D’endL
D’endH
D’orL
D’orH
QuoL
QuoH
RemL
RemH
16Bit x 16Bit
MD0
MD4
MD1
MD5
MD0
MD1
MD2
MD3
M’andL
M’orL
M’andH
M’orH
PrL
PrH