Rainbow Electronics MAX5131 - Manual (Page 12)

MAX5130/MAX5131
The 16-bit input word may be sent in two 1-byte pack-
ets (SPI-, MICROWIRE- and PIC16/PIC17-compatible),
with CS low during this period. The control bits C2, C1,
and C0 (Table 1) determine:
•
The clock edge on which DOUT is to be clocked out
via the serial interface,
•
The state of the user-programmable logic output,
•
The configuration of the device after shutdown.
The general timing diagram in Figure 6 illustrates how
data is acquired. CS must be low for the part to receive
data. With CS low, data at DIN is clocked into the regis-
ter on the rising edge of SCLK. When CS transitions
high, data is latched into the input and/or DAC registers,
depending on the setting of the three control bits C2,
C1, and C0. The maximum serial clock frequency guar-
anteed for proper operation is 10MHz for the MAX5130
and 6.6MHz for the MAX5131. Figure 7 depicts a more
detailed timing diagram of the serial interface.
Table 2. Serial Data Format
PIC16 with SSP Module and
PIC17 Interface
The MAX5130/MAX5131 are compatible with a
PIC16/PIC17 microcontroller (µC), using the synchro-
nous serial port (SSP) module. To establish SPI com-
munication, connect the controller as shown in Figure 4
and configure the PIC16/PIC17 as system master by
initializing its synchronous serial port control register
(SSPCON) and synchronous serial port status register
(SSPSTAT) to the bit patterns shown in Tables 3 and 4.
In SPI mode, the PIC16/PIC17 µCs allow 8 bits of data
to be transmitted synchronously and received simulta-
neously. Two consecutive 8-bit writings (Figure 6) are
necessary to feed the DAC with three control bits and
13 data bits. DIN data transitions on the serial clock’s
falling edge and is clocked into the DAC on SCLK’s ris-
ing edge. The first 8 bits on DIN contain the three con-
trol bits (C2, C1, and C0) and the first five data bits
(D12–D8). The second 8-bit word contains the remain-
ing bits (D7–D0).
+3V/+5V, 13-Bit, Serial Voltage-Output DACs
with Internal Reference
12 ______________________________________________________________________________________
Control Bits MSB ..... Data Bits ..... LSB
MSB ............................................................................... LSB
⇐ 16 BITS OF SERIAL DATA ⇒
D12................................D0 C2, C1, C0
CS
SCLK
DIN
COMMAND
EXECUTED
9 8 16 1
C1 C2 D0 C0 D12 D11 D10 D9 D6 D5 D4 D3 D2 D1 D8 D7
Figure 6. Serial-Interface Timing
SCLK
DIN
DOUT
t
CS0
t CSS
t CL
t CH
t CP
t CSW
t CS1
t CSH
t
DS t DO1 t DO2
t
DH
CS
Figure 7. Detailed Serial-Interface Timing