User's Manual

Chapter 2 Configuration and Installation

The following signals are used in the timing diagrams shown later in this chapter:

Pin Direction Description

STB* Input Strobe Input—A low signal on this handshaking line loads data into the

input latch.

IBF Output Input Buffer Full—A high signal on this handshaking line indicates that

data has been loaded into the input latch. This is basically an input

acknowledge signal.

ACK* Input Acknowledge Input—A low signal on this handshaking line indicates

that the data written from the specified port has been accepted. This

signal is basically a response from the external device that it has received

the data from the Lab-NB.

OBF* Output Output Buffer Full—A low signal on this handshaking line indicates that

data has been written from the specified port.

INTR Output Interrupt Request—This signal becomes high when the 82C55A is

requesting service during a data transfer. The appropriate interrupt

enable signals must be set to generate this signal.

RD* Internal Read Signal—This signal is the read signal generated from the control

lines of the NuBus.

WR* Internal Write Signal—This signal is the write signal generated from the control

lines of the NuBus.

DATA Bidirectional Data Lines at the Specified Port—This signal indicates when the data on

the data lines at a specified port is or should be available.