Pmod LVLSHFT Reference Manual

The Digilent Pmod LVLSHFT (Revision B) is a digital logic level shifter. This module is ideal for users who want to supply logic signals following a 3.3V CMOS standard but have an alternate logic level output that is used for other applications such as JTAG programming.

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Features

  • Digital logic level shifter
  • Translate logic signals between two user supplied voltage levels
  • 2×7 JTAG header
  • 8 miniature switches to dictate logic level conversion
  • Voltage range between 1.8V and 5.5V
  • 12-pin Pmod port with GPIO interface

Functional Description

The Pmod LVLSHFT translates logic signals between two user supplied voltage levels. Users can use a small object such as a pen or a screwdriver to adjust the switches for the direction of the voltage translation.


Interfacing with the Pmod

The Pmod LVLSHFT communicates with the host board via GPIO. Users can supply any form of digital signals to either end of the Pmod and have them translated to the other voltage level. Switches are provided to indicate the direction of the voltage translation. A switch pushed to the left side (green) towards the pin header translates voltages from VCCB to VCCA; a switch on the right side (yellow) towards the JTAG header translates from VCCA to VCCB.

Pmod LVLSHFT Voltage Translation directions (click to enlarge)

A pinout table for the Pmod LVLSHFT is provided below:

Pin Descriptions for the Pmod LVLSHFT
Header J1 JTAG Header J2 Header J3
Pin Signal Description Pin Signal Description Pin Signal Description
1 AIO1/TMS A1 & TMS JTAG pin 1 GND Power Supply Ground 1 BIO1/TMS B1 & TMS JTAG pin
2 AIO2/TDI A2 & TDI JTAG pin 2 VCCB Power Supply side B 2 BIO5/SRST B5 & Signal Reset pin
3 AIO3/TDO A3 & TDO JTAG pin 3 GND Power Supply Ground 3 BIO2/TDI B2 & TDI JTAG pin
4 AIO4/TCK A4 & TCK JTAG pin 4 BIO1/TMS B1 & TMS JTAG pin 4 BIO6 I/O pin B6
5 GND Power Supply Ground 5 GND Power Supply Ground 5 BIO3/TDO B3 & TDO JTAG pin
6 VCCA Power Supply side A 6 BIO4/TCK B4 & TCK JTAG pin 6 BIO7 I/O pin B7
7 AIO5 I/O pin A5 7 GND Power Supply Ground 7 BIO4/TCK B4 & TCK JTAG pin
8 AIO6 I/O pin A6 8 BIO3/TDO B3 & TDO JTAG pin 8 BIO8 I/O pin B8
9 AIO7 I/O pin A7 9 GND Power Supply Ground Header J4
10 AIO8 I/O pin A8 10 BIO2/TDI B2 & TDI JTAG pin Pin Signal Description
11 GND Power Supply Ground 11 GND Power Supply Ground 1 VCCB Power Supply side B
12 VCCA Power Supply side A 12 (NC) Not Connected 2 GND Power Supply Ground
13 GND Power Supply Ground
14 SRST Signal Reset

Note* Headers J2 and J3 follow the JTAG pin numbering convention as opposed to the Pmod header numbering convention

Any external power applied to the Pmod LVLSHFT must be within 1.8V and 5.5V.


Physical Dimensions

The pins on the pin header are spaced 100 mil apart. The PCB is 1.75 inches long on the sides parallel to the pins on the pin header and 0.8 inches long on the sides perpendicular to the pin header.


Additional Information

The schematics of the Pmod LVLSHFT are available here. The datasheet for Texas Instruments SN47LVC1T45 which is used in this Pmod is available here.

As a passthrough module, there is no code available to properly demonstrate how to use the Pmod LVLSHFT.

If you have any questions or comments about the Pmod LVLSHFT, feel free to post them under the appropriate section (“Add-on Boards”) of the Digilent Forum.