Function:

Reads values from a port address in DX into a string at ES:DI or ES:EDI
in memory. When used with the REPcondition prefix, CX or ECX contains the
number of values to read.

There is also a NEC specific instruction with the conflicting mnemonic INS,
see <NECINS> or select <NEC specific instructions> from the mnemonic list
page for more information regarding that instruction.

Bugs in the 286;
If, in protected mode, ES would contain a null selector or ES:DI would
point beyond the segment limit when executing the single INS, causing
exception 0dh, the 0d exception handler would point to the instruction
following INS and not to it.

If, in protected mode, during the repeated version of the instruction, a
segment limit or IOPL exception occurred, the exception handler would see
the CX value as it was before the start of the instruction, DI would reflect
the proper index at the time of the exception though. This type of bug
also occurs with the CMPS instruction.

Bugs in the 386:
The value of CX or ECX after the REPcondition version is not correct when
the instruction is followed by a PUSH, POP or memory reference. After
REP INS the value of CX, ECX is -1, not 0. Do not assume (E)CX to be 0.

When REP INS or INS is followed by an instruction that uses a different
address size or when they are followed by an instruction that references
the stack implicitly while the B bit of the SS descriptor is different than
the address size used by the instruction, INS will not properly update
the (E)DI and REP INS will not properly update the (E)CX register.
The actual address size used will be the one of the instruction following
the (REP) INS.
A workaround for this bug is to code a NOP with the same address size as the
INS right behind it by using the address size prefix byte 67h (when needed).

Bugs in the 486:
Early 486 may hang if the INS destination address spans across a doubleword
boundary, while not asserting BS16# or BS8#.
To avoid this, always align the string at a doubleword.




INS  (NECINS) Insert bit field (NEC V20/30 only)
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