Rainbow Electronics MAX5302 - Manual (Page 7)

MAX5302
Low-Power, 12-Bit Voltage-Output DAC
with Serial Interface
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SCLK
DIN
CS
SK
SO
I/O
MAX5302
MICROWIRE
PORT
Figure 2. Connections for MICROWIRE
DIN
SCLK
CS
MOSI
SCK
I/O
SPI/QSPI
PORT
SS
+5V
CPOL = 0, CPHA = 0
MAX5302
Figure 3. Connections for SPI/QSPI Figure 4. Serial-Data Format
3 Control
Bits
12+1 Data Bits
D11 .....................................D0, S0 C2 C1 C0
Data Bits
MSB ................................LSB Sub-Bit
Control
Bits
16 Bits of Serial Data
MSB ..................................................................................LSB
S0
Table 1. Serial-Interface Programming Commands
X = Don’t care
16-BIT SERIAL WORD
0 1 1
X 0 0
X 0 1
X 1 0
1 1 1
No operation (NOP)
Load input register; DAC register immediately updated (also exit shutdown).
D11...............D0
MSB
LSB
FUNCTION
Load input register; DAC register unchanged.
C2 C1 C0
Update DAC register from input register (also exit shutdown; recall previ-
ous state).
Shutdown
XXXXXXXXXXXX
12 bits of data
12 bits of data
XXXXXXXXXXXX
XXXXXXXXXXXX
S0
0
0
X
X
X
by updating the DAC with new data. When powering up
the device or bringing it out of shutdown, allow 20µs for
the output to stabilize.
Serial-Interface Configurations
The MAX5302’s 3-wire serial interface is compatible
with both MICROWIRE (Figure 2) and SPI/QSPI (Figure 3).
The serial-input word consists of 3 control bits followed
by 12+1 data bits (MSB first), as shown in Figure 4. The
3-bit control code determines the MAX5302’s response
outlined in Table 1.
The MAX5302’s digital inputs are double buffered.
Depending on the command issued through the serial
interface, the input register can be loaded without
affecting the DAC register, the DAC register can be
loaded directly, or the DAC register can be updated
from the input register (Table 1).
Serial-Interface Description
The MAX5302 requires 16 bits of serial data. Table 1 lists
the serial-interface programming commands. For certain
commands, the 12+1 data bits are “don’t cares.” Data is
sent MSB first and can be sent in two 8-bit packets or
one 16-bit word (CS must remain low until 16 bits are
transferred). The serial data is composed of 3 control