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Netlist entry
Axxxx s r clk set reset out nout model_name
Connection details
Name
Description
Flow
Type
s
S input
in
d
r
R input
in
d
clk
Clock
in
d
set
Asynchronous set
in
d
reset
Asynchronous reset
in
d
out
Data output
out
d
nout
Inverted data output
out
d
Model format
.MODEL model_name d_srff parameters
Model parameters
Name
Description
Type
Default
Limits
clk_delay
Delay from clk
real
1nS
???MATH???1\text{e}^{-12} - \infty???MATH???
set_delay
Delay from set
real
1nS
???MATH???1\text{e}^{-12} - \infty???MATH???
reset_delay
Delay from reset
real
1nS
???MATH???1\text{e}^{-12} - \infty???MATH???
ic
Output initial state
integer
0
0 - 2
rise_delay
Rise delay
real
1nS
???MATH???1\text{e}^{-12} - \infty???MATH???
fall_delay
Fall delay
real
1nS
???MATH???1\text{e}^{-12} - \infty???MATH???
sr_load
S,r load values (F)
real
1pF
none
clk_load
Clk load value (F)
real
1pF
none
set_load
Set load value (F)
real
1pF
none
reset_load
Reset 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
real
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
Device Operation
The SR flip flop is similar to a JK flip flop except that the output is UNKNOWN when both S and R inputs are high. In a JK the output toggles in the same circumstances.
The following table describes the operation of the device when both inputs are at known states: The output can only change on a positive edge on the clock.
S input
R input
Output
0
0
No change
0
1
0
1
0
1
1
1
UNKNOWN
When either input is UNKNOWN, the situation is more complicated. There are some circumstances when a known state can be clocked to the output even if one of the inputs is unknown. The following table describes the operation for possible input states. X means UNKNOWN.
S input
R input
old output
new output
0
0
0
0
0
0
1
1
0
0
X
X
0
1
0
0
0
1
1
0
0
1
X
0
0
X
0
0
0
X
1
X
0
X
X
X
1
0
0
1
1
0
1
1
1
0
X
1
1
1
0
X
1
1
1
X
1
1
X
X
1
X
0
X
1
X
1
X
1
X
X
X
X
0
0
X
X
0
1
1
X
0
X
X
X
1
0
X
X
1
1'
X
X
1
X
X
X
X
0
X
X
X
1
X
X
X
X
X
◄ Random Access Memory
SR Latch ▶