NEC uPD98502 SDL Store Doubleword Left (1/3) SDL

APPENDIX A MIPS III INSTRUCTION SET DETAILS
540 Preliminary User’s Manual S15543EJ1V0UM
SDL Store Doubleword Left (1/3) SDL
base
SDL
1 0 1 1 0 0 rt offset
31 26 25 21 20 16 15 0
655 16
Format:
SDL rt, offset (base)
Description:
This instruction can be used with the SDR instruction to store the contents of a register into eight consecutive bytes
of memory, when the bytes cross a doubleword boundary. SDL stores the register into the appropriate part of the
high-order doubleword of memory; SDR stores the register into the appropriate part of the low-order doubleword.
The SDL instruction adds its sign-extended 16-bit
offset to the contents of general register base to form a virtual
address that may specify an arbitrary byte. It alters only the word in memory that contains that byte. From one to
four bytes will be stored, depending on the starting byte specified.
Conceptually, it starts at the most-significant byte of the register and copies it to the specified byte in memory; then
it copies bytes from register to memory until it reaches the low-order byte of the word in memory.
No address error exceptions due to alignment are possible.
address 8
address 0
memory
15 14 13 12 11 10 9 8
76543210 A B C D E F G H
before
after
$24
register
SDL $24, 8 ($0)
address 8
address 0
15 14 13 12 11 10 9 A
76543210