MAX5478EVKIT Maxim Integrated, MAX5478EVKIT Datasheet - Page 6

• Manufacturer Part Number: MAX5478EVKIT
• Description: Digital Potentiometer ICs Evaluation Kit/Evaluation System for the MAX5477/MAX5478/MAX5479
• Manufacturer: Maxim Integrated

Specifications of MAX5478EVKIT

• Resistance: 50 kOhms
• Number Of Pots: Dual
• Taps Per Pot: 256
• Wiper Memory: Non Volatile
• Digital Interface: Serial (2-Wire, I2C)
• Operating Supply Voltage: 5 V
• Supply Current: 15 uA
• Supply Voltage - Max: 5.25 V
• Supply Voltage - Min: 2.7 V

The MAX5478 EV kit software automatically searches for
the MAX5478 during startup using the eight possible
addresses. If the software finds the MAX5478 digital
potentiometer, the Status indicator shows the MAX5478
is operational or if it is not found, the Status indicator
shows that the MAX5478 was not found and the Device
Address is set to “??”. Select the Auto Detect option
from the Device Address combo box to search for the
device address.
Use the I
speed to 400kHz or 100kHz.
There are two methods for communicating with the
MAX5478 EV kit; through the normal user-interface
panel (Figure 1) or by using low-level I
available through the 2-Wire Interface Diagnostic
(Figure 2) item from the main program’s Options main
menu. A window is displayed that allows I
such as Read Byte and Write Byte. The Read Byte
operation is not used because the MAX5478 does not
send data to the master. To stop normal user-interface
execution so that it does not override the manually set
values, turn off the update timer by unchecking the
Automatic Diagnostics checkbox in the MAX5478
main program.
Note: To ensure a fail-safe write-protect feature, write
the data to be protected to the nonvolatile and volatile
registers before pulling WP high (WP = 1). Releasing
WP (WP = 0) and sending invalid I
as single-byte address polling) can load the volatile reg-
ister with corrupted data and change the wiper position.
Use valid 3-byte I
MAX5478 Evaluation Kit/Evaluation System
Table 3. Write-Protect Behavior of VREG and NVREG
Note: While WP = 1, the MAX5478 EV kit software may display incorrect memory data because the potentiometer is a write-only
device.
SMBus is a trademark of Intel Corporation.
6
Write to the volatile
memory VREG
Write to the nonvolatile
memory NVREG
Copy NVREG to VREG
Copy VREG to NVREG
_______________________________________________________________________________________
COMMAND
2
C Bus Speed combo box to set the bus
2
C commands for proper operation.
I
Wiper position updates with I
No change to NVREG.
No change to VREG or wiper position.
I
Copy NVREG to VREG.
Wiper position updates with NVREG data.
No change to NVREG.
Copy VREG to NVREG.
No change to VREG or wiper position.
2
2
C data is written to VREG.
C data is written to NVREG.
Simple I
WRITE PROTECT DISABLED (WP = 0)
2
C commands (such
2
C Commands
2
2
C commands
C operations,
Interface
2
C data.
The I
decimal, or hexadecimal. Hexadecimal numbers
should be prefixed by $ or 0x. Binary numbers must be
exactly eight digits. See Figure 2 for an example of this
tool. Figure 2 shows a simple SMBus™ write-byte oper-
ation using the included 2-wire interface diagnostics
tool. In this example, the software is writing data 0xB8
to the register address 0x11 (Potentiometer A volatile
memory) of the device with device address 0x5E. The
above data sequence sets wiper A position of the
MAX5478 to position 113.
Problem: Software reports it cannot find the board.
• Is the CMODUSB command module power LED
• Is the USB communications cable connected?
• Has Windows plug-and-play detected the board?
Problem: Unable to find device under test (DUT)
• Is power connected to the MAX5478 EV kit?
• Are the SCL and SDA signals pulled up to VDD
• If using jumper wires to connect, could the SCL and
(LED1) lit?
Bring up Control Panel, then System, then Device
Manager, and look at what device nodes are indicat-
ed for USB. If there is an “unknown device” node
attached to the USB, delete it. This forces plug-and-
play to try again.
through appropriate resistors (2.4kΩ typ)? The
CMODUSB command module dip switch SW1
enables the on-board resistors. There must be pullup
resistors somewhere on the I
SDA signals be swapped? Could the ground return
be missing?
2
C dialog boxes accept numeric data in binary,
Copy NVREG to VREG.
Wiper position updates with NVREG data.
No change to NVREG.
No change to VREG or wiper position.
No change to NVREG.
Copy NVREG to VREG.
Wiper position updates with NVREG data.
No change to NVREG.
No change to VREG or wiper position.
No change to NVREG.
WRITE PROTECT ENABLED (WP = 1)
General Troubleshooting
2
C bus.