Renesas rl78 User Manual

RL78/G1A

CHAPTER 14 MULTIPLIER AND DIVIDER/MULTIPLY-ACCUMULATOR

14.2.2 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 14-3. Format of Multiplication/Division Data Register B (MDBH, MDBL)

Address: FFFF4H, FFFF5H, FFFF6H, FFFF7H After reset: 0000H, 0000H R/W

Symbol

FFFF5H

FFFF4H

MDBH

Symbol

FFFF7H

FFFF6H

MDBL

MDBHL

MDBL

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 14-3. Functions of MDBH and MDBL Registers During Operation Execution

Operation Mode

Setting

Operation Result

Multiplication mode (unsigned)

Multiply-accumulator mode (unsigned)

−

MDBH: Multiplication result (product) (unsigned)

Higher 16 bits

MDBL: Multiplication result (product) (unsigned)

Lower 16 bits

Multiplication mode (signed)

Multiply-accumulator mode (signed)

−

MDBH: Multiplication result (product) (signed)

Higher 16 bits

MDBL: Multiplication result (product) (signed)

Lower 16 bits

Division mode (unsigned)

MDBH: Divisor (unsigned)

(higher 16 bits)

MDBL: Divisor (unsigned)

(lower 16 bits)

−

R01UH0305EJ0200 Rev.2.00

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Jul 04, 2013