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b90fdbb | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 | # Standard Parasitic Exchange Format (SPEF)
OpenTimer reads parasitics of a net set as a resistive-capacitive (RC) network.
Each RC network is described in a [Standard Parasitic Exchange Format (SPEF)][SPEF Wiki] file.
If the connection does not have parasitics, then the delay is zero and the output
slew is euqal to the input slew.
# Admissible SPEF Format
OpenTimer can parse pretty much a complete SPEF netlist.
We use the open-source project [Parser-SPEF][Parser-SPEF] to parse a SPEF file.
Each SPEF file contains:
1. header section
2. name map section
3. port section
4. parasitics section
```spef
// begin header (14 lines)
*SPEF <string>
*DESIGN <string>
*DATE <string>
*VENDOR <string>
*PROGRAM <string>
*VERSION <string>
*DESIGN_FLOW <string>
*DIVIDER <string>
*DELIMITER <string>
*BUS_DELIMITER <string>
*T_UNIT <int> <string>
*C_UNIT <int> <string>
*R_UNIT <int> <string>
*L_UNIT <int> <string>
// name-map section
*NAME_MAP
*1 node_name_1
*2 node_name_2
*3 node_name_3
...
// port section
port_name_1 direction
...
// parasitics section
*D_NET net_name total_net_capacitance
*CONN
pin_type pin_name pin_direction
...
*CAP
integer_label node_name node_capacitance
...
*RES
integer_label node_name node_name node_resistance
...
*END
```
## Example
The example below demonstrates a valid SPEF file for OpenTimer.
```
*SPEF "IEEE 1481-1998"
*DESIGN "simple"
*DATE "Tue Aug 30 09:15:30 2017"
*VENDOR "OpenTimer"
*PROGRAM "OpenTimer"
*VERSION "0.0"
*DESIGN_FLOW "NETLIST_TYPE_VERILOG"
*DIVIDER /
*DELIMITER :
*BUS_DELIMITER [ ]
*T_UNIT 1 PS // 1 pico second
*C_UNIT 1 FF // 1 femto farad
*R_UNIT 1 KOHM // 1 killo ohm
*L_UNIT 1 UH
*NAME_MAP
*1 inp2 // replace all "*1" with inp2 hereafter
*D_NET *1 2.0 // *D_NET inp2 2.0
*CONN
*P *1 I // *P inp2 I
*I u1:b I
*CAP
1 *1 0.2 // 1 inp2 0.2
2 *1:1 0.5 // 2 inp2:1 0.5
3 *1:2 0.4 // 3 inp2:2 0.4
4 u1:b 0.9
*RES
1 *1 *1:1 1.4 // 1 inp2 inp2:1 1.4
2 *1:1 *1:2 1.5 // 2 inp2:1 inp2:2 1.5
3 *1:2 u1:b 1.6 // 3 inp2:2 u1:b 1.6
*END
```
<p>
<img src="spef_example.png" width="60%">
Parasitics of net inp2.
</p>
The example above defines a RC network `inp2` with a total lumped
capacitance of 2 femto farads (fF). The name mapped section defines:
+ `inp2` to be referred by its name or by \*1
The connection section defines:
+ Port pin `inp2` with input direction
+ Internal pin `u1:b` with input direction
`inp2` as a primary input port and `u1:b` as an internal input pin.
The capacitor section defines:
+ 0.2 fF capacitor between primary input pin `inp2` and `GND`
+ 0.5 fF capacitor between SPEF-specific intermediate node `inp2:1` and `GND`
+ 0.4 fF capacitor between SPEF-specific intermediate node `inp2:2` and `GND`
+ 0.9 fF capacitor between `u1:b` and `GND`
The resistor section defines:
+ 1.4 kOhm resistor between primary input pin `inp2` and `inp2:1`
+ 1.5 kOhm resistor between SPEF-specific intermediate nodes `inp2:1` and `inp2:2`
+ 1.6 kOhm resistor between SPEF-specific intermediate node `inp2:2` and `u1:b`
# Reference
1. [Standard Parasitic Exchange Format][SPEF Wiki]
2. [2015 ACM TAU Timing Analysis Contest][TAU15]
* * *
[SPEF Wiki]: https://en.wikipedia.org/wiki/Standard_Parasitic_Exchange_Format
[Parser-SPEF]: https://github.com/OpenTimer/Parser-SPEF
[TAU15]: https://sites.google.com/site/taucontest2015/
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