Instruction manual

Table Of Contents
PC215E Page 32
BIT ASSIGNMENTS
The bit layout of the PPI-Y port B data register is shown below.
5.3.7 Programmable Peripheral Interface PPI-Y Data Register Port C
This eight bit register writes to and reads from port C of the 82C55 Programmable Peripheral
Interface PPI-Y. All input/output lines PC0 to PC7 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
0A
16
Write and Read 8 bits
82C55 Programmable Peripheral
Interface Y Port C Data Register
PPI-Y C
FUNCTION
The PPI-Y Port C Data Register is used to write or read 8 bit data to a port of the 82C55
Programmable Peripheral Interface device
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 C are split into two groups, the upper port C bits 4 to 7 and the lower
port C bits 0 to 3. These bits can be data input, data output or control/handshake lines according
to the PPI mode:
Mode Port C Upper Port C Lower
Mode 0 Input or Output Input or Output
Mode 1 Control/Data Control/Data
Mode 2 5 bit Control (PC3 to PC7) 3 bit Control/Data (PC0 to PC2)
With bit 7 'Command Select' set to '0', any of the eight bits of port C can be set or reset using a
single output instruction. When port C is being used as status/control for port A or port B, these
bits can be set or reset using the Bit Set/Reset operation just as if they were data output ports.
01234567
PPI-Y Port B Digital
I/O Data Bits
Digital I/O SK1
Pin Connections
SK1 72
SK1 33
SK1 52
SK1 13
SK1 71
SK1 32
SK1 51
SK1 12
PB0
PB1
PB2
PB3
PB4
PB5
PB6
PB7