0

17kviews

Explain I/O related addressing mode of 8086.

written 8.0 years ago by meghalikalyankar • 2.3k

•   modified 4.0 years ago

microprocessors and applications

ADD COMMENT FOLLOW SHARE EDIT

1 Answer

3

1.1kviews

written 8.0 years ago by meghalikalyankar • 2.3k

1. The 8086 can generate 16-bit of I/O address. Thus it can address up to 64 Kbyte I/O locations or 32 K word I/O locations.
2. The 16-bit I/O address appears on A_0 to A_15 address lines; A_16 to A_19 lines are at logic 0 during the I/O operations.
3. The 16-bit DX register is used as 16-bit I/O address pointer to address up to 64 IC devices in in-direct addressing mode.
4. The 1/0 instructions with direct addressing mode can directly address one or two of the 256 I/O byte locations in page 0 of the 1/0 address space.

1. I/0 ports are addressed in the same manner as memory locations. Even addressed bytes are transferred on the D_7-D_0 bus lines and odd addressed bytes onD_15-D_8.
2. Care must be taken to assure that each register within an 8-bit peripheral located on the lower portion of the bus be addressed as even.
3. In the I/O space, Intel has reserved 00F8H to 00FF locations.

ADD COMMENT SHARE EDIT