Instruction manual

AMPDIO DRIVERS
Page 67
BIT ASSIGNMENTS
The bit layout of the PPI-X port B data register is shown below.
7 6 5 4 3 2 1 0
PPI-X Port B Digital
I/O Data Bits
SK1 46
SK1 7
SK1 65
SK1 26
SK1 45
SK1 6
SK1 64
SK1 25
Digital I/O SK1
Pin Connections
PB0
PB1
PB2
PB3
PB4
PB5
PB6
PB7
5.4.1.3 82C55 Programmable Peripheral Interface PPI Data Register Port C
This eight-bit register writes to and reads from port C of the 82C55 Programmable Peripheral
Interface PPI.
Register
Offset
Write and/or
Read
Register
Width
Register
Title
Mnemonic
02
16
Write and Read 8 bits
82C55 Programmable
Peripheral Interface Port C
Data Register
PPI C
FUNCTION
The PPI 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 on the SOFTMAN CD.
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.
A full description of the operating modes and all other features of the 82C55 are available in the
manufacturer’s data sheet for the 82C55, available on the SOFTMAN CD.