ST STEVAL-PCC003V1, Руководство пользователя, Страница: 16 / 29

Pin assignments UM0529
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5.5.1 Decoder/demultiplexer U2
Table 10 shows the truth table for the first input of U2.
Thus, it can be seen by comparing column 3 (input 1A) and column 5 (output Y1), that the
USBOE signal is getting inverted.
Table 11 shows the truth table for the second input of U2.
Thus, it can be seen by comparing column 3 (input 2A) and column 4 (output Y0), that the
SUS signal is getting buffered. Hence only the voltage level conversion from 5 V to 3.3 V is
done.
5.5.2 Decoder/demultiplexer U3
The first input and other related input pins are not connected in this decoder. Table 13
shows the truth table for second input of U3.
Table 10. Truth table for first input of U2
Inputs Outputs
Enable Select
n1G(1) 1B(3) = GND 1A(2)= USBOE nY0(4) = NC nY1 (5) = nUSBOE nY2(6)= NC nY3(7) = NC
H X X H H H H
L L L L H H H
L L H H L H H
Table 11. Truth table for second input of U2
Inputs Outputs
Enable Select
n2G(15) 2B(13)=GND 2A(14) = SUS_5 nY0(12) =SUS_33 nY1(11)= NC nY2(10) = NC nY3(9) = NC
H x X H H H H
L L L L H H H
L L H H L H H
Table 12. Truth table for first input of U3
Inputs Outputs
Enable Select
N1G(1) 1B(3) = GND 1A(24) = CON-5V nY0(4) =CON-3V3 nY1(5) = NC nY2(6) = NC nY3(7) = NC
H x X H H H H
L L L L H H H
L L H H L H H
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