Rainbow Electronics MAX1273 - Manual (Page 15)

MAX1272/MAX1273
Fault-Protected, 12-Bit ADCs
with Software-Selectable Input Range
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CS
SCLK
DOUT
I/O
SCK
MISO
SPI
SS
MAX1272
MAX1273
V DD
Figure 10a. SPI Connections
MAX1272
MAX1273
CS
SCLK
DOUT
I/O
SCK
SI
MICROWIRE
Figure 10b. MICROWIRE Connections
QSPI Interface
Using the high-speed QSPI interface with CPOL = 0
and CPHA = 0, the MAX1272/MAX1273 support a max-
imum f
SCLK
of 1.4MHz. Figure 11 shows the MAX1272/
MAX1273 connected to a QSPI master.
PIC16 with SSP Module and
PIC17 Interface
The MAX1272/MAX1273 are compatible with a
PIC16/PIC17 controller (µC) using the synchronous ser-
ial-port (SSP) module.
To establish SPI communication, connect the controller
as shown in Figure 12 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 5 and 6.
In SPI mode, the PIC16/PIC17 µCs allow 8 bits of data
to be transmitted and received simultaneously. Three
consecutive 8-bit readings are necessary to obtain the
entire 12-bit result from the ADC. DOUT data transitions
on the serial clock’s falling edge and is clocked into the
µC on SCLK’s rising edge. The first 8-bit data stream
contains all zeros. The second 8-bit data stream con-
tains a leading zero followed by the MSB through D5.
The third 8-bit data stream contains bits D4–D0 fol-
lowed by trailing zeros.
Transfer Function
Output data coding for the MAX1272/MAX1273 is bina-
ry in unipolar mode with:
and two’s complement binary in bipolar mode with:
Code transitions occur halfway between successive
integer LSB values. Figures 13a and 13b show the
input/output transfer functions for uni-polar and bipolar
operations, respectively. For full-scale (FS) values, see
Tables 2 and 3.
1
2
4096
LSB
FS
=
× | |
1
4096
LSB
FS
=
CS
SCLK
DOUT
CS
SCK
MISO
QSPI V
DD
SS
MAX1272
MAX1273
Figure 11. QSPI Connections
I/O
SCLK
DOUT
GND
SCK
SDI
PIC16/PIC17
V DD V DD
MAX1272
MAX1273
CS
Figure 12. SPI Interface Connection for a PIC16/PIC17