Texas Instruments SN74AXC4T774, Руководство пользователя, Страница: 3 / 7

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Introduction
3 SCEU015 – May 2019
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Copyright © 2019, Texas Instruments Incorporated
SN74AXC4T774 Evaluation Module User Guide
Figure 1. SPI/JTAG Translation using SN74AXC4T774EVM
1.2 Hardware Description
1.2.1 Headers
The EVM has standard 100-mil headers with the side closer to the device connected to ground. The side
farther away from the device is mapped to the device pinout for easier connection as seen in
Figure 1 .
The silkscreen indicates the pin name.
1.2.2 Bypass Capacitors
C1, and C2 are the bypass capacitors for V
CCA
while C3, and C4 are the bypass capacitors for V
CCB
with a
value of 0.1 µF.
1.2.3 Pull-up and Pull-down Resistors
The direction control and output enable pins are the inputs for the devices and should never be left
floating. The CMOS inputs must be held at a known state, either V
CC
or ground, to ensure proper device
operation. Refer to Implications of Slow or Floating CMOS Inputs ( SCBA004 ).
Table 2 lists the pull-up and pull-down resistors and their default states.
1.2.4 SMB Connectors
The edge-mounted SMB connector pair for supporting high-speed operation are provided on data I/O pins
of A2 and B2, while the corresponding header pin has an uninstalled R11 and R12 resistor.