MAX5550 Maxim Integrated Products, MAX5550 Datasheet - Page 12

• Manufacturer Part Number: MAX5550
• Description: High-Output-Current DAC
• Manufacturer: Maxim Integrated Products

In standard SPI-/QSPI™-/MICROWIRE™-compatible
systems, a microcontroller (µC) communicates with its
slave devices through a 3- or 4-wire serial interface.
The typical interface includes a chip-select signal (CS),
a serial clock (SCLK), a data input signal (DIN), and
sometimes a data signal output (DOUT). In this system,
the µC allots an independent slave-select signal (SS_)
to each slave device so that they can be addressed
individually. Only the slaves with their CS inputs assert-
ed low acknowledge and respond to the activity on the
serial clock and data lines. This is simple to implement
when there are very few slave devices in the system.
An alternative method is daisy chaining. Daisy
Dual, 10-Bit, Programmable, 30mA
High-Output-Current DAC
12
Figure 6. SPI-Interface Timing Diagram
Figure 7. SPI-Interface Format
CS
SCLK
DOUT
DIN
______________________________________________________________________________________
SCLK
DIN
CS
t
CSO
Applications Information
Daisy Chaining (SPI/ I2C = V
t
CSE
t
1
CSS
C5
t
DS
2
MSB
C4
t
DH
3
C3
t
MSB
CH
4
C2
t
CP
5
C1
t
DO1
6
C0
t
CL
DD
7
D9
)
8
D8
chaining, in serial-interface applications, is the method
of propagating commands through devices connected
in series (see Figure 8).
Daisy chain devices by connecting the DOUT of one
device to the DIN of the next. Connect the SCLK of all
devices to a common clock and connect the CS of all
devices to a common slave-select line. Data shifts out of
DOUT 16.5 clock cycles after it is shifted into DIN on the
falling edge of SCLK. In this configuration, the µC only
needs three signals (SS, SCK, and MOSI) to control all of
the slaves in the network. The SPI-/QSPI-/MICROWIRE-
compatible serial interface normally works at up to
10MHz, but must be slowed to 5MHz if daisy chaining.
DOUT is high impedance when CS is high.
QSPI is a trademark of Motorola, Inc.
MICROWIRE is a trademark of National Semiconductor Corp.
LSB
D7
9
10
D6
D5
11
t
CSH
12
D4
D3
13
14
D2
t
CS1
t
CSD
D1
15
t
CSW
16
D0