Rainbow Electronics MAX5233 - Manual (Page 12)

MAX5232/MAX5233
Serial Interface
The 3-wire serial interface (SPI, QSPI, MICROWIRE
compatible) used in the MAX5232/MAX5233 allows for
complete control of DAC operations (Figures 4 and 5).
Figures 1 and 2 show the timing for the serial interface.
The serial word consists of 3 control bits followed by 10
data bits (MSB first) and 1 sub-bit as described in
Tables 1, 2, and 3. When the three control bits are all
zeros or all 1, D9–D6 are used as additional control
bits, allowing for greater DAC functionality.
The digital inputs allow any of the following: loading the
input register(s) without updating the DAC register(s),
updating the DAC register(s) from the input register(s),
or updating the input and DAC register(s) simultane-
ously. The control bits and D9–D6 allow the DACs to
operate independently.
Send the 16-bit data as one 16-bit word (QSPI) or two
8-bit packets (SPI, MICROWIRE), with CS low during
this period. The control bits and D9–D6 determine
which registers update and the state of the registers
when exiting shutdown. The 3-bit control and D9–D6
determine the following:
• Registers to be updated
• Selection of the power-down and shutdown modes
The general timing diagram of Figure 1 illustrates data
acquisition. Driving CS low enables the device to
receive data. Otherwise the interface control circuitry is
disabled. With CS low, data at DIN is clocked into the
register on the rising edge of SCLK. As CS goes high,
data is latched into the input and/or DAC registers,
depending on the control bits and D9–D6. The maxi-
mum clock frequency guaranteed for proper operation
is 13.5MHz. Figure 2 depicts a more detailed timing
diagram of the serial interface.
3V/5V, 10-Bit, Serial Voltage-Output Dual DACs
with Internal Reference
12 ______________________________________________________________________________________
Table 1. Serial Data Format
MSB <------------16-bits of serial data ------------> LSB
3 Control Bits MSB .. 10 Data Bits ... LSB Sub-Bit
C2…C0 D9 ................................D0 S2, S1, S0
Table 2. Serial-Interface Programming Commands
16-BIT SERIAL WORD
C2 C1 C0 D9..............D0 S2–S0
FUNCTION
0 0 1 10-bit DAC data 000 Load input register A; DAC registers are unchanged.
0 1 0 10-bit DAC data 000 Load input register A; all DAC registers are updated.
0 1 1 10-bit DAC data 000
Load all DAC registers from the shift register (start up both DACs with
new data, and load the input registers).
1 0 0 X X X X X X X X X X 000
Update both DAC registers from their respective input registers (start
up both DACs with data previously stored in the input registers).
1 0 1 10-bit DAC data 000 Load input register B; DAC registers are unchanged.
1 1 0 10-bit DAC data 000 Load input register B; all DAC registers are updated.
1 1 1 P1A P1B X X X X X X X X 000
Shut down both DACs, respectively, according to bits P1A and P1B
(see Table 3). Internal bias and reference remain active.
0 0 0 0 0 1 X X X X X X X 000
Update DAC register A from input register A (start up DAC A with
data previously stored in input register A).
0 0 0 0 1 1 P1A P1B X X X X X 000
Full Power-Down. Power down the main bias generator and shut
down both DACs, respectively, according to bits P1A and P1B (see
Table 3).
0 0 0 1 0 1 X X X X X X X 000
Update DAC register B from input register B (start up DAC B with
data previously stored in input register B).
0 0 0 1 1 0 P1A X X X X X X 000 Shut down DAC A according to bit P1A (see Table 3).
0 0 0 1 1 1 P1B X X X X X X 000 Shut down DAC B according to bit P1B (see Table 3).
0 0 0 1 0 0 0 X X X X X X 000 Mode 0. DOUT clocked out on SCLK falling edge (default).
0 0 0 1 0 0 1 X X X X X X 000 Mode 1. DOUT clocked out on SCLK rising edge.
X = Don’t care.
* S0 must be zero for proper operation.