Renesas rl78 User Manual

RL78/G1A

CHAPTER 14 MULTIPLIER AND DIVIDER/MULTIPLY-ACCUMULATOR

14.2.1 Multiplication/division data register A (MDAH, MDAL)

The MDAH and MDAL registers set the values that are used for a multiplication or division operation and store the

operation result. They set the multiplier and multiplicand data in the multiplication mode or multiply-accumulator mode,

and set the dividend data in the division mode. Furthermore, the operation result (quotient) is stored in the MDAH and

MDAL registers in the division mode.

The MDAH and MDAL registers can be set by a 16-bit manipulation instruction.

Reset signal generation clears these registers to 0000H.

Figure 14-2. Format of Multiplication/Division Data Register A (MDAH, MDAL)

FFFF3H

FFFF2H

MDAH

FFFF1H

FFFF0H

MDAL

Address:

FFFF0H, FFFF1H, FFFF2H, FFFF3H After reset: 0000H, 0000H R/W

Symbol

Cautions 1. Do not rewrite the MDAH and MDAL registers values during division operation processing (when

the multiplication/division control register (MDUC) value is 81H or C1H). The operation will be

executed in this case, but the operation result will be an undefined value.

2. The MDAH and MDAL registers values read during division operation processing (when the

MDUC register value is 81H or C1H) will not be guaranteed.

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 MDAH and MDAL registers during operation execution.

Table 14-2. Functions of MDAH and MDAL Registers During Operation Execution

Operation Mode

Setting

Operation Result

Multiplication mode (unsigned)

Multiply-accumulator mode (unsigned)

MDAH: Multiplier (unsigned)

MDAL: Multiplicand (unsigned)

−

Multiplication mode (signed)

Multiply-accumulator mode (signed)

MDAH: Multiplier (signed)

MDAL: Multiplicand (signed)

−

Division mode (unsigned)

MDAH: Dividend (unsigned)

(higher 16 bits)

MDAL: Dividend (unsigned)

(lower 16 bits)

MDAH: Division result (unsigned)

Higher 16 bits

MDAL: Division result (unsigned

Lower 16 bits

R01UH0305EJ0200 Rev.2.00

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Jul 04, 2013