Analog Devices UG-442, User Manual

Page: 7 / 16

Evaluation Board User Guide UG-442
Rev. C | Page 7 of 16
The main window is divided into eight sections: Input Register ,
Status Register
,
Control Register
,
Reset Register
,
Clear/Clear
Select Pins , Read/Write Registers , Measure Output Voltage/
Current , and Program Voltage/Current.
Input Register
The Input Register section displays the contents of the input
register. The 24-bit display is updated each time a read or a
write operation is requested via the main window controls. It
allows users to associate the value written to the
AD5422 with
the various programmable functions.
Status Register
The Status Register section displays the states of the three bits
of the read-only status register. To read the register, click the
Read Status Register button.
Control Register
The Control Register section facilitates programming of the
control register on an individual bit basis. To change the value
for a bit, click the relevant button. Each button also displays the
current state of the bit. You can also enter code in the
SR CLOCK
and SR STEP text boxes and select an output range from the
OUTPUT RANGE drop-down box.
When using an external current setting resistor, it is recom-
mended to only set REXT when also setting the OUTEN bit.
Alternately, REXT can be set before the OUTEN bit is set, but
the range must be changed on the write in which the output is
enabled. The Read/Write Registers section should be used for
these commands (see Figure 4).
Reset Register
The sole function of the Reset Register section is to allow the
AD5422 to be reset to its power-on state. To change the value of
the reset bit, click the RESET button.
Clear Pin
In the Clear/Clear Select Pins section, you can change the state
of the CLEAR pin by clicking the CLEAR button. Likewise, you
can change the state of the CLEAR SELECT pin by clicking the
CLEAR SELECT button.
Read/Write Registers
In the Read/Write Registers section, you can read from and write
to all registers in the AD5422 . To select a register and request a
read or write, click the Select Control Function drop-down
box. Then, to write data to the register, select the desired data
from the
Data Write drop-down box and then click OK . Register
data is updated and displayed for you to read in the Data Read
text box each time you click OK .
Measure Output Voltage/Current
To display the programmed output current in the Measure Output
Current section, click the Measure output Current button. The
output current is measured using the on-board ADC and is
displayed in milliamperes in the
V
OUT
or I
OUT
box. The output
current is measured with an accuracy of approximately 1% and is
therefore not intended as precise, but rather is an approximate
feedback of the programmed value.
Program Current
To program a voltage or current output value, enter the value in
either volts or milliamperes (mA) in the
Enter Value text box of
the Program Voltage/Current section, and press Enter . The
output must first be enabled, and the output range must be
selected via the
Control Register section.
0
823
0-
3
00
POWER-ON
SOFTWARE RESET
CONTROL REGISTER WRITE (ONE WRITE COMMAND)
• SELECT R
SET
EXTERNAL/INTERNAL
• SET THE REQUIRED RANGE
• CONFIGURE THE SLEW RATE CONTROL (IF REQUIRED)
• CONFIGURE DAISY CHAIN MODE (IF REQUIRED)
• ENABLE THE OUTPUT
DATA REGISTER WRITE
• WRITE REQUIRED CODE TO DATA REGISTER
CONTROL REGISTER WRITE
• DISABLE OUTPUT
R
SET
CONFIGURATION CHANGE RANGE CHANGE
Figure 4. Programming Sequence to Write/Enable the Output Correctly