FSTUD162450 Datasheet, PDF (4/11 Pages) Fairchild Semiconductor – Configurable 4-Bit to 20-Bit Bus Switch with -2V Undershoot Protection and Selectable Level Shifting and 25Ω Series Resistors in Outputs

Functional Description
The device can also be configured as an 8 and 16-bit device by grounding the unused pins in the 10-bit and 20-bit configu-
rations respectively. The 8-bit configuration may also be achieved by connecting two of the 4-bit enables from the 4-bit con-
figuration together and connecting the remaining enable pin (OE) HIGH.
Truth Tables
(see Functional Description)
S2
L
H
Select Pin
Mode
Std. NMOS Switch
Level Shifting Diode Enabled
20-Bit Configuration (S₀ = S₁ = L)
Inputs
OE₁
OE₂
OE₃
OE₄
OE₅
L
X
X
X
X
H
X
X
X
X
Inputs/Outputs
1A_1-10 = 1B_1-10, 2A_1-10 = 2B_1-10
Z
10-Bit Configuration (S₀ = L, S₁ = H)
Inputs
OE₁
OE₂
OE₃
OE₄
OE₅
L
X
X
L
X
L
X
X
H
X
H
X
X
L
X
H
X
X
H
X
Inputs/Outputs
1A_1-10 = 1B_1-10
1A_X = 1B_X
1A_X = 1B_X
Z
Z
2A_1-10 = 2B_1-10
2A_X = 2B_X
Z
2A_X = 2B_X
Z
5-Bit Configuration (S₀ = H, S₁ = L)
Inputs
OE₁ OE₂ OE₃ OE₄ OE₅
L
L
L
L
X
L
L
L
H
X
L
L
H
L
X
L
L
H
H
X
L
H
L
L
X
L
H
L
H
X
L
H
H
L
X
L
H
H
H
X
H
L
L
L
X
H
L
L
H
X
H
L
H
L
X
H
L
H
H
X
H
H
L
L
X
H
H
L
H
X
H
H
H
L
X
H
H
H
H
X
1A_1-5, 1B_1-5
1A_x = 1B_x
1A_x = 1B_x
1A_x = 1B_x
1A_x = 1B_x
1A_x = 1B_x
1A_x = 1B_x
1A_x = 1B_x
1A_x = 1B_x
Z
Z
Z
Z
Z
Z
Z
Z
Inputs/Outputs
1A_6-10, 1B_6-10
1A_y = 1B_y
1A_y = 1B_y
1A_y = 1B_y
1A_y = 1B_y
Z
Z
Z
Z
1A_y = 1B_y
1A_y = 1B_y
1A_y = 1B_y
1A_y = 1B_y
Z
Z
Z
Z
2A_1-5, 2B_1-5
2A_x = 2B_x
2A_x = 2B_x
Z
Z
2A_x = 2B_x
2A_x = 2B_x
Z
Z
2A_x = 2B_x
2A_x = 2B_x
Z
Z
2A_x = 2B_x
2A_x = 2B_x
Z
Z
2A_6-10, 2B_6-10
2A_y = 2B_y
Z
2A_y = 2B_y
Z
2A_y = 2B_y
Z
2A_y = 2B_y
Z
2A_y = 2B_y
Z
2A_y = 2B_y
Z
2A_y = 2B_y
Z
2A_y = 2B_y
Z
www.fairchildsemi.com
4