请问Primetime报告中的Z、A、B、C是怎么回事？谢谢

请问Primetime报告中的Z、A、B、C是怎么回事?他们分别代表什么含义，各自的数值都是怎么来的?谢谢各位大侠
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Report : delay_calculation
Design : RISC_CORE
Version: D-2009.12-SP1
Date: Mon Mar 14 05:27:31 2016
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From pin: I_DATA_PATH/Oprnd_B_reg[3]/CLK
To pin:I_DATA_PATH/Oprnd_B_reg[3]/Q
Main Library Units:1ns1pF1kOhm
Library: 'ssc_core_slow'
Library Units:1ns1pF1kOhm
Library Cell: 'fdesf1a9'
arc sense:rising_edge
arc type:cell
Units:1ns1pF1kOhm

Rise Delay
cell delay = 0.617072
Table is indexed by
(X) input_pin_transition = 0
(Y) output_net_total_cap = 0.0885082
Relevant portion of lookup table:
(X)0.0280(X)0.0570
(Y)0.0620(Z)0.5860(Z)0.5960
(Y)0.1160(Z)0.6680(Z)0.6770
Z = A + B*X + C*Y + D*X*Y
A =0.4811B =0.3844
C =1.5364D = -0.6386
Z = 0.617072
scaling result for operating conditions
multiplying by 1 gives 0.617072
Fall Delay
cell delay = 0.536889
Table is indexed by
(X) input_pin_transition = 0
(Y) output_net_total_cap = 0.0885082
Relevant portion of lookup table:
(X)0.0280(X)0.0570
(Y)0.0620(Z)0.5220(Z)0.5330
(Y)0.1160(Z)0.5730(Z)0.5830
Z = A + B*X + C*Y + D*X*Y
A =0.4517B =0.4189
C =0.9623D = -0.6386
Z = 0.536889
scaling result for operating conditions
multiplying by 1 gives 0.536889
Cell Delay
rise:0.617072
fall:0.536889
Rise delay = 0.617072
Fall delay = 0.536889
Units:1ns1pF1kOhm
Transition rise
transition = 0.319435
Table is indexed by
(X) input_pin_transition = 0
(Y) output_net_total_cap = 0.0885082
Relevant portion of lookup table:
(X)0.0280(X)0.0570
(Y)0.0620(Z)0.2360(Z)0.2350
(Y)0.1160(Z)0.4040(Z)0.4030
Z = A + B*X + C*Y + D*X*Y
A =0.0441B = -0.0345
C =3.1111D = -0.0000
Z = 0.319435
scaling result for operating conditions
multiplying by 1 gives 0.319435

Transition fall
transition = 0.18629
Table is indexed by
(X) input_pin_transition = 0
(Y) output_net_total_cap = 0.0885082
Relevant portion of lookup table:
(X)0.0280(X)0.0570
(Y)0.0620(Z)0.1480(Z)0.1470
(Y)0.1160(Z)0.2250(Z)0.2250
Z = A + B*X + C*Y + D*X*Y
A =0.0617B = -0.0741
C =1.4080D =0.6386
Z = 0.18629
scaling result for operating conditions
multiplying by 1 gives 0.18629

Rise transition = 0.319435
Fall transition = 0.18629
1

同求~同求~