Renesas rl78 User Manual

 

RL78/G1A 

CHAPTER  14   MULTIPLIER  AND  DIVIDER/MULTIPLY-ACCUMULATOR 

 

• Initial setting 

<1>  Set the multiplication/division control register (MDUC) to 08H. 

<2>  Set the multiplicand to multiplication/division data register A (L) (MDAL). 

<3>  Set the multiplier to multiplication/division data register A (H) (MDAH). 

 

(There is no preference in the order of executing steps <2> and <3>.  Multiplication operation is automatically 

started when the multiplier and multiplicand are set to the MDAH and MDAL registers, respectively.) 

•  During operation processing 

<4>  Wait for at least one clock.  The operation will end when one clock has been issued. 

• Operation end 

<5>  Read the product (lower 16 bits) from multiplication/division data register B (L) (MDBL). 

<6>  Read the product (higher 16 bits) from multiplication/division data register B (H) (MDBH). 

(There is no preference in the order of executing steps <5> and <6>.) 

• Next operation 

<7>  Start with the initial settings of each step to change the operation mode.  When the same operation mode is 

used sequentially, settings <1> and <2> can be omitted. 

 

Caution  The data is in the two's complement format in multiplication mode (signed). 

Remark  Steps <1> to <7> correspond to <1> to <7> in Figure 14-7. 

 

−2 × 32767 = −65534) 

 

MDAL

FFFFH

FFFFH

0000H
0001H

FFFEH

7FFFH

FFFFH

0002H

00H

08H

MDAH

MDBH

MDBL

MDUC

MDSM

8001H

FFFFH

<2>

<1>

<3>

<5>, <6>

<4>

<7>

0000H

0000H

0000H
0000H

Operation clock

 

R01UH0305EJ0200  Rev.2.00 

 

 

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Jul 04, 2013