Specifications

78 Chapter 4—Simulation
The Port Interface
The connection between a pin on a parent device symbol and the corre-
sponding signal in the internal circuit is quite complex, from a simulation
standpoint. In order for this connection to act like a “hard wire” between
the two levels, the following conditions must be met:
 The pin type on the parent device symbol must be “bidirectional.”
 The pin type of the corresponding port connector in the internal circuit
must be “bidirectional.”
 The pin delays on both the pin on the parent device and the pin on the
port connector must be zero.
 No pin inversion must be specified, either on the parent device pin or
the port connector pin.
Any other combination of settings will result in some degree of isolation or
“buffering” between the two levels. For example, The observed signal
value on the signal in the internal circuit may be different from that on the
parent pin.
NOTE: When a symbol is created in the DevEditor tool, all pins default to type
“input”—that is, they will not drive any attached signal. If you are creating a
subcircuit device symbol for simulation purposes, the pin types must be set
to appropriate values.
The effects of these various settings are summarized in the following sec-
tions.
Parent Device Pin Type
Any signal value driven out of a parent pin by an internal circuit may be
translated according to the pin type on the parent device. These effects are
summarized in the following table.
LW Reference.bk Page 78 Monday, December 15, 2003 5:59 PM