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Rainbow Electronics MAX5155 User Manual

Page 11

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The MAX5154/MAX5155’s digital inputs are double
buffered, which allows 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 registers concurrently.
The address and control bits allow the DACs to act
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 address and control bits determine which
register will be updated, and the state of the registers
when exiting shutdown. The 3-bit address/control deter-
mines the following:

• registers to be updated

• clock edge on which data is to be clocked out via

the serial-data output (DOUT)

• state of the user-programmable logic output

• configuration of the device after shutdown.

The general timing diagram of Figure 5 illustrates how
data is acquired. 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 address and control bits. The maxi-
mum clock frequency guaranteed for proper operation
is 10MHz. Figure 6 depicts a more detailed timing dia-
gram of the serial interface.

MAX5154/MAX5155

Low-Power, Dual, 12-Bit Voltage-Output DACs

with Serial Interface

DIN

SCLK

CS

MOSI

SCK

I/O

SPI/QSPI

PORT

SS

+5V

CPOL = 0, CPHA = 0

MAX5154
MAX5155

Figure 3. Connections for SPI/QSPI

Figure 5. Serial-Interface Timing Diagram

CS

SCLK

DIN

COMMAND

EXECUTED

9

8

16

1

C1

A0

S0

C0

D11 D10

D9

D8

D5

D4

D3

D2

D1

D0

D7

D6

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11

Figure 4. Serial-Data Format

1 Address/2 Control Bits

A0

Address Bits

C1, C0

Control Bits

12 Data Bits

D11.......................D0

MSB...DataBits...LSB

0

S0

SUB

BIT

16 Bits of Serial Data

MSB...................................................................................LSB