RL78/G13 CHAPTER 14 MULTIPLIER AND DIVIDER/MULTIPLY-ACCUMULATOR
R01UH0146EJ0100 Rev.1.00 794
Sep 22, 2011
14.4.3 Multiply-accumulation (unsigned) operation
• Initial setting
<1> Set the multiplication/division control register (MDUC) to 40H.
<2> Set the initial accumulated value of higher 16 bits to multiplication/division data register C (L) (MDCL).
<3> Set the initial accumulated value of lower 16 bits to multiplication/division data register C (H) (MDCH).
<4> Set the multiplicand to multiplication/division data register A (L) (MDAL).
<5> Set the multiplier to multiplication/division data register A (H) (MDAH).
(There is no preference in the order of executing steps <2>, <3>, and <4>. Multiplication operation is
automatically started when the multiplier is set to the MDAH register, respectively.)
• During operation processing
<6> The multiplication operation finishes in one clock cycle.
(The multiplication result is stored in multiplication/division data register B (L) (MDBL) and multiplication/division
data register B (H) (MDBH).)
<7> After <6>, the multiply-accumulation operation finishes in one additional clock cycle. (There is a wait of at least
two clock cycles after specifying the initial settings is finished (<5>).)
• Operation end
<8> Read the accumulated value (lower 16 bits) from the MDCL register.
<9> Read the accumulated value (higher 16 bits) from the MDCH register.
(There is no preference in the order of executing steps <8> and <9>.)
(<10> If the result of the multiply-accumulation operation causes an overflow, the MACOF bit is set to 1, INTMD
signal is occurred.)
• Next operation
<11> To execute multiply-accumulation (unsigned) operation next, start from the “Initial setting” for multiply-
accumulation (unsigned) operation.
<12> The next time multiplication (signed or unsigned), multiply-accumulation (signed), or division is performed, start
with the initial settings of each step.
Remark Steps <1> to <10> correspond to <1> to <10> in Figure 14-8.
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