Instruction manual

Table Of Contents
PC215E Page 30
Command Word for Bit Set/Reset Format
5.3.5 Programmable Peripheral Interface PPI-Y Data Register Port A
This eight bit register writes to and reads from port A of the 82C55 Programmable Peripheral
Interface PPI-Y. All input/output lines PA0 to PA7 of this device are available to the user on
connector SK1 as digital I/O.
Register
Offset
Write and/or
Read
Register
Width
Register
Title
Mnemonic
08
16
Write and Read 8 bits
82C55 Programmable Peripheral
Interface Y Port A Data Register
PPI-Y A
FUNCTION
The PPI-X Port A Data Register is used to write or read 8 bit data to port A of the 82C55
Programmable Peripheral Interface device PPI-Y.
The PPI can be configured to operate in several modes. Further details may be found by
reference to the device manufacturer's 82C55 data sheets in the appendices.
The eight data bits of port A are data input, data output or bi-directional data I/O according to the
PPI mode:
Mode 0 Input or Output
Mode 1 Input or Output
Mode 2 Bi-Directional Input/output
The modes and programming of PPI operations are outlined in chapters 4 and 6 with the Digital
I/O connections shown in chapter 3.
01234567
Bit Set/Reset 0 = Reset
1 = Set
Port C Bit Select
Bit Set/Reset Flag
0 = Active
COMMAND
SELECT
6 74 52 30 1
0 B
0
10 10 10 1
1 B
1
10 0
1 1
0 0
1 B
2
11 10 00 0
X X X
Don't Care