User manual

Chapter 3 Signal Connections

Table 3-2. Timing Signal Descriptions

Name Type 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 an input

acknowledge signal.

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

indicates that the data written to the port has been accepted. This

signal is a response from the external device indicating that it has

received the data from the PC-DIO-96/PnP.

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

indicates that data has been written to the port.

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

requests service during a data transfer. The appropriate interrupt

enable bits must be set to generate this signal.

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

control lines of the computer I/O expansion bus.

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

control lines of the computer I/O expansion bus.

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

availability of data on the data lines at a port that is in the output

mode. If the port is in the input mode, this signal indicates when the

data on the data lines should be valid.