Dual-Interface Wrap Test
Original Publication Date: 1994-Jun-01
Included in the Prior Art Database: 2005-Mar-27
Bergey, AL: AUTHOR [+3]
Disclosed is a wrap test for master-slave half-duplex interface with differential drivers.
Dual-Interface Wrap Test
a wrap test for master-slave half-duplex interface
with differential drivers.
This invention is a test mechanism for the interface shown in Fig. 1.
The interface contains the following signals, as shown in Fig. 1.
1. Two byte-wide data transfer busses
control signals to provide control information from the
master to the slave.
3. Inbound control
signals to provide control information from the
slave to the master.
All of these signals use differential drivers and receivers.
The interface works in one of two operating modes:
1. For command and
status transfer, one of the two byte-wide data
transfer busses (bus 0) is configured for transfer from the
master to the slave, while the other (bus 1) is configured for
transfer from the slave to the master. These busses, together
with the Controls In/Out are controlled by microcode. This
allows full-duplex, relatively slow transfer of information
between the master and the attached slave.
2. For data
transfer, both data transfer busses are configured to go
in the same direction (from master to slave for WRITE, from slave
to master for READ). These busses, together with the control
lines, are controlled by data transfer hardware. This allows
half-duplex, high-speed transfer of information between the
master and the attached slave (Fig. 2).
and status transfer mode has been tested with wrap
techniques for many years. Wrap-testing a full-duplex, microcode
controlled interface is not difficult. Bus 0 wraps to Bus 1, and the
Control Out signals wrap to the Control In signals. This is shown in
testing this interface only in its full-duplex
configuration is not sufficient to ensure a high quality product.
The full-duplex configuration does not test all parts of the hardware
and does not test them at high speed. A test of the interface in the
half-duplex data transfer mode is required to fully exercise the
In the past,
data transfer mode testing has been done either
with a real slave, or with a simulator. The master under test is
cables to the slave or slave simulator, and data is transferred to or
from it using the data transfer protocol. This technique has certain
1. A slave or
slave simulator costs money. Letting the
itself costs only the expense of a wrap cable. This represents a
significant manufacturing cost savings.
In spite of
these advantages, no one has successfully tested
the interface data transfer mechanism using a wrap technique. This
is due to the following difficulties:
1. The interface
data transfer mechanism is a half-duplex mechanism.
It transfers data from the master, or to the master, but never
both at the same time.
Wrap tests must have both...