Changes

8255

No change in size, 28 March

/* PPI Control */

This register has two different functions depending on bit7 of the data written to this register.

=== PPI Control with Bit7=0 ===

Otherwise, if Bit 7 is "0" then the register is used to set or clear a single bit in Port C:

Bit 0 B New value for the specified bit (0=Clear, 1=Set)

Bit 1-3 N0,N1,N2 Specifies the number of a bit (0-7) in Port C

Bit 4-6 - Not Used

Bit 7 SF Must be "0" in this case

[[File:Intel 8255A - BSR control word format.jpg]]

=== PPI Control with Bit7=1 ===

[[File:Intel 8255A - IO modes control word format.jpg]]

~~=== PPI Control with Bit7=0 ===~~

~~Otherwise, if Bit 7 is "0" then the register is used to set or clear a single bit in Port C:~~

~~Bit 0 B New value for the specified bit (0=Clear, 1=Set)~~

~~Bit 1-3 N0,N1,N2 Specifies the number of a bit (0-7) in Port C~~

~~Bit 4-6 - Not Used~~

~~Bit 7 SF Must be "0" in this case~~

~~[[File:Intel 8255A - BSR control word format.jpg]]~~

== Programming Examples ==

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