Simulator Reference: Buffer

Netlist entry

Axxxx in out model_name

Connection details

Name	Description	Flow	Type
in	Input	in	d
out	Output	out	d

Model format

.MODEL model_name d_buffer parameters

Model parameters

Name	Description	Type	Default	Limits
rise_delay	Rise delay	real	1nS	1e-12 ???MATH???- \infty???MATH???
fall_delay	Fall delay	real	1nS	1e-12 ???MATH???- \infty???MATH???
stored_delay	Stored delay (overrides rise_delay and fall_delay)	real	0	???MATH???0 - \infty???MATH???
input_load	Input load value (F)	real	1pF	none
family	Logic family	string	UNIV	none
in_family	Input logic family	string	UNIV	none
out_family	Output logic family	string	UNIV	none
out_res	Digital output resistance	real	100	???MATH???0 - \infty???MATH???
out_res_pos	Digital output res. pos. slope	real	out_res	???MATH???0 - \infty???MATH???
out_res_neg	Digital output res. neg. slope		out_res	???MATH???0 - \infty???MATH???
open_c	Open collector output	boolean	FALSE	none
min_sink	Minimum sink current	real	-0.001	none
max_source	Maximum source current	real	0.001	none
sink_current	Input sink current	real	0	none
source_current	Input source current	real	0	none
open_e	Open emitter output	boolean	FALSE	none

Device Operation

This device is a simple buffer with a single input and output. It can optionally be specified to have an open collector (open_c parameter) or open emitter (open_e parameter) output. Further, if the stored_delay parameter is specified, the device will act as a pure delay. This means that it will pass pulses that are shorter than the delay time whereas normally (delay specified by rise_delay and fall_delay) such pulse would be swallowed (stored_delay is also known as transport delay).

The following table describes the device operation in detail

OPEN_C parameter	OPEN_E parameter	Input	Output state	Output strength
FALSE	FALSE	0	0	STRONG
FALSE	FALSE	1	1	STRONG
FALSE	FALSE	UNKNOWN	UNKNOWN	STRONG
FALSE	TRUE	0	0	HI-IMPEDANCE
FALSE	TRUE	1	1	STRONG
FALSE	TRUE	UNKNOWN	UNKNOWN	UNDETERMINED
TRUE	FALSE	0	0	STRONG
TRUE	FALSE	1	0	HI-IMPEDANCE
TRUE	FALSE	UNKNOWN	0	UNDETERMINED
TRUE	TRUE	0	1	HI-IMPEDANCE
TRUE	TRUE	1	0	HI-IMPEDANCE
TRUE	TRUE	UNKNOWN	UNKNOWN	UNDETERMINED

Note the difference between open emitter and open collector operation. These modes have been designed to be as close to as possible to real devices, in particular their behaviour into an open circuit. An open emitter output, when switching from high to low is likely to follow the voltage on the device's base due to the base-emitter capacitance so the output state follows the input state. An open collector (or open drain) output on the other hand will remain in the low state when its input switches.