Renesas RL78 Series User Manual page 648

RL78/G1D
16.2.2 Multiplication/division data register B (MDBL, MDBH)
The MDBH and MDBL registers set the values that are used for multiplication or division operation and store the
operation result. They store the operation result (product) in the multiplication mode and multiply-accumulator mode, and
set the divisor data in the division mode.
The MDBH and MDBL registers can be set by a 16-bit manipulation instruction.
Reset signal generation clears these registers to 0000H.
Figure 16-3. Format of Multiplication/Division Data Register B (MDBH, MDBL)
Address: FFFF4H, FFFF5H, FFFF6H, FFFF7H
Symbol
MDBH MDBH MDBH
15 14
Symbol
MDBL MDBL MDBL
15 14
Cautions 1. Do not rewrite the MDBH and MDBL registers values during division operation processing
(when the multiplication/division control register (MDUC) value is 81H or C1H) or multiply-
accumulation operation processing. The operation result will be an undefined value.
2. Do not set the MDBH and MDBL registers to 0000H in the division mode. If they are set, the
operation result will be an undefined value.
3. The data is in the two's complement format in either the multiplication mode (signed) or
multiply-accumulator mode (signed).
The following table shows the functions of the MDBH and MDBL registers during operation execution.
Table 16-3. Functions of MDBH and MDBL Registers During Operation Execution
Operation Mode
Multiplication mode (unsigned)
Multiply-accumulator mode (unsigned)
Multiplication mode (signed)
Multiply-accumulator mode (signed)
Division mode (unsigned)
R01UH0515EJ0120 Rev.1.20
Dec 16, 2016
CHAPTER 16 MULTIPLIER AND DIVIDER/MULTIPLY-ACCUMULATOR
After reset: 0000H, 0000H R/W
FFFF5H
MDBH MDBH MDBH MDBH
13 12 11 10
FFFF7H
MDBL MDBL MDBL MDBL
13 12 11 10
Setting
MDBH: Divisor (unsigned)
(higher 16 bits)
MDBL: Divisor (unsigned)
(lower 16 bits)
MDBH MDBH MDBH MDBH
9 8 7 6
MDBL MDBL MDBL MDBL
9 8 7 6
– MDBH: Multiplication result (product) (unsigned)
MDBL: Multiplication result (product) (unsigned)
– MDBH: Multiplication result (product) (signed)
MDBL: Multiplication result (product) (signed)
FFFF4H
MDBH MDBH MDBH MDBH
5 4 3 2
FFFF6H
MDBL MDBL MDBHL MDBL
5 4 3 2
Operation Result
Higher 16 bits
Lower 16 bits
Higher 16 bits
Lower 16 bits
–
MDBH MDBH
1 0
MDBL MDBL
1 0
627