Specifications

Using Subcircuits 51
Note that it contains two symbols, both representing subcircuit devices.
Both symbols are of the same type, RSFF, and therefore share the same
internal circuit definition. The two devices are named FF1 and FF2. Open-
ing either one of these devices reveals the following internal circuit:
This circuit consists of three device symbols, G1, G2, and G3, representing
physical devices, and a number of port connector symbols. The port con-
nectors define the interface between the internal circuit and the pins on the
symbol representing it.
Note the following characteristics of this simple design:
 The device RSFF has been used twice, so there are actually two G1s,
one inside FF1 and one inside FF2. We say that there are two instances
of G1. Similarly for G2 and G3.
 The signals SET/, RESET, and Q in the internal circuit will actually get
absorbed into the attached signals in the parent circuit because they are
attached to port connectors. They do not exist independently in the
physical circuit.
LW Reference.bk Page 51 Monday, December 15, 2003 5:59 PM