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30 FUJITSU MICROELECTRONICS LIMITED CM71-00105-1E
CHAPTER 3 PROGRAMMING MODEL
3.3
The reset value of table base register (TBR) is 000F FC00
H
. Do not set a value above FFFF FC00
H
for the
table base register (TBR).
Precautions:
If values greater than FFFF FC00
H
are assigned to the table base register (TBR), this operation may
result in an overflow when summed with the offset value. An overflow in turn will result in vector
access to the area 0000 0000
H
to 0000 03FF
H
, which can cause a program run away.
3.3.12 Multiplication/Division Register (MDH, MDL)
Multiplication/Division register (MDH, MDL) is a 64-bit register comprised of MDH represented by the
higher 32 bits and MDL represented by the lower 32 bits. During multiplication, the product is stored.
During division, the value set for the dividend and the quotient is stored.
Figure 3.3-18 shows the bit configuration of Multiplication/Division register (MDH, MDL).
Figure 3.3-18 Multiplication/Division Register (MDH, MDL) Bit Configuration
The function of Multiplication/Division register (MDH, MDL) is different during a multiplication and
during a division operation.
● Function during Multiplication
In case of a 32 bit × 32 bit multiplication (MUL, MULU instruction), the calculation result of 64-bit length
is stored in the product register (MDH, MDL) as follows.
MDH: higher 32 bits
MDL: lower 32 bits
In case of a 16 bit × 16 bit multiplication (MULH, MULUH instruction), the calculation result of 32-bit
length is stored in the product register (MDH, MDL) as follows.
MDH: undefined
MDL: result 32 bits
Figure 3.3-19 shows an example of multiplication operation using Multiplication/Division register (MDH,
MDL).
MDH
MDL
bit31 bit0
Initial value
XXXXXXXX
XXXXXXXX
H
H