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CHAPTER 7 DETAILED EXECUTION INSTRUCTIONS
7.40 DIV1 (Main Process of Division)
This instruction is used in unsigned division. It should be used in combinations such as
DIV0U and DIV1 x 32.
■ DIV1 (Main Process of Division)
Assembler format: DIV1 Ri
Operation: {MDH, MDL} < < = 1
if (D1 = = 1) {
MDH + Ri → temp
}
else {
MDH – Ri → temp
}
if ((D0 eor D1 eor C) = = 0) {
temp → MDH
1 → MDL [0]
}
Flag change:
N and V: Unchanged
Z: Set when the result of step division is "0", cleared otherwise. Set according to remainder of
division results, not according to quotient.
C: Set when the operation result of step division involves a carry operation, cleared otherwise.
Execution cycles: d cycle(s)
Normally executed within one cycle. However, a 2-cycle interlock is applied if the instruction
immediately after is one of the following: MOV MDH, Ri / MOV MDL, Ri / ST Rs, @-R15.
Rs : dedicated register (TBR, RP, USP, SSP, MDH, MDL)
Instruction format:
NZVC
–C–C
MSB LSB
100101110110 Ri