The Genius of Amstrad I/O Addresses (Blog Article)

[McArti0]

https://dn790009.ca.archive.org/0/items/Zilog_Z80-CPU_Technical_Manual/Zilog_Z80-CPU_Technical_Manual.pdf

page 35 manual 1976

[McArti0]

page 54

opcode list

B-> A8-A15

in 1976.

[McArti0]

Note that the I/O port address is duplicated onto both AD0-AD7 and A8-A15

http://www.bitsavers.org/components/intel/MCS80/MCS80_85_Users_Manual_Jan83.pdf  page 35  (2-12)  About 8085A



OUT 0-255

About 8080, page 68 (4-4)

So only the Z80 was able to handle 16bits? Not even the 8085 in a useful way?

Note that the I/O port address is duplicated onto both AD0-AD7 and A8-A15

http://www.bitsavers.org/components/intel/MCS80/MCS80_85_Users_Manual_Jan83.pdf  page 35  (2-12)  About 8085A



OUT 0-255

About 8080, page 68 (4-4)

So only the Z80 was able to handle 16bits? Not even the 8085 in a useful way?

8085 can be justified, because it has a data bus multiplexed with addresses. AD0-AD7. Copy A0-A7 to A8-A15 allowed easy use of IO with disentangled addresses from data. So I guess everyone used 8085 IO from A8-A15.

[GUNHED]

It is totally wrong, that the Z80 only had 8 bit I/O addresses. Sounds like click-bait

Zilog disagrees: "I/O device at one of 256 possible ports".

Don't thrust these guys, they discontinued producing the chip 

[pelrun]

"hey, the high byte is hooked up for IO but if we just say that the market will decide we're not actually 8080 compatible... put the truth later in the datasheet since the managers won't read that far"