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■ User Stack Pointer (USP)
Function of user stack pointer (USP: User Stack Pointer) is described.
The user stack pointer (USP) consists of 32-bit.
Figure 3.3-6 shows the bit configuration of the user stack pointer (USP).
Figure 3.3-6 User stack pointer (USP)
USP is the user stack pointer.
When the S flag is "1", the USP functions as R15. The USP can be specified explicitly. The initial value by
reset is irregular.
The USP cannot be used for the RETI instruction.
■ Multiplication and Division Result Register (MDH/MDL)
Function of multiplication and division result register (MDH/MDL: Multiply & Divide register) is
described.
The multiplication and division result register (MDH/MDL) consists of 32-bit.
Figure 3.3-7 shows the bit configuration of the multiplication and division result register (MDH/MDL).
Figure 3.3-7 Multiplication and division result storage register (MDH/MDL)
MDH and MDL are the multiplication and division register. Each register is 32-bit long.
The initial value by reset is irregular.
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Functions when multiplication is executed
In the case of 32-bit x 32-bit multiplication, the 64-bit long operation results are stored in the
multiplication/division results register in the following format.
• MDH: Higher 32-bit
• MDL: Lower 32-bit
In the case of 16-bit x 16-bit multiplication, the results are stored in the multiplication/division results
register as follows.
• MDH: Indeterminate
• MDL: 32-bit
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Functions when division is executed
When beginning to calculate, the dividend is stored in MDL.
When division is calculated using the DIV0S/DIV0U, DIV1, DIV2, DIV3, or DIV4S commands, the
results are stored in the MDL and MDH as follows.
• MDH: surplus
• MDL: commerce
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H
31 0 Initial value
bit
31 0
bit
MDH
MDL
Initial value
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H
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