Rainbow Electronics MAX1111 - Manual (Page 15)

MAX1110/MAX1111
+2.7V, Low-Power, Multichannel,
Serial 8-Bit ADCs
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SCLK
DIN
DOUT
CS
S CONTROL BYTE 0 CONTROL BYTE 1 S
CONVERSION RESULT 0
B7 B0 B7 B0 B7
CONVERSION RESULT 1 CONVERSION RESULT 2
SSTRB
CONTROL BYTE 2 S
1 8 8 8 10 1 10 1 10 1
CONTROL BYTE 3 S
Figure 12a. Continuous Conversions, External Clock Mode, 10 Clocks/Conversion Timing
CS
SCLK
DIN
DOUT
S CONTROL BYTE 0 CONTROL BYTE 1 S
CONVERSION RESULT 0
B7 B0 B7
CONVERSION RESULT 1
Figure 12b. Continuous Conversions, External Clock Mode, 16 Clocks/Conversion Timing
Data Framing
The falling edge of CS does not start a conversion. The
first logic high clocked into DIN is interpreted as a start
bit and defines the first bit of the control byte. A conver-
sion starts on the falling edge of SCLK, after the eighth
bit of the control byte (the PD0 bit) is clocked into DIN.
The start bit is defined as:
The first high bit clocked into DIN with CS low any
time the converter is idle; e.g., after V
DD is applied.
OR
The first high bit clocked into DIN after the MSB of a
conversion in progress is clocked onto the DOUT
pin.
If CS is toggled before the current conversion is com-
plete, then the next high bit clocked into DIN is recog-
nized as a start bit; the current conversion is
terminated, and a new one is started.
The fastest the MAX1110/MAX1111 can run is 10
clocks per conversion. Figure 12a shows the serial-
interface timing necessary to perform a conversion
every 10 SCLK cycles in external clock mode.
Many microcontrollers require that conversions occur in
multiples of eight SCLK clocks; 16 clocks per conver-
sion is typically the fastest that a microcontroller can
drive the MAX1110/MAX1111. Figure 12b shows the
serial-interface timing necessary to perform a conver-
sion every 16 SCLK cycles in external clock mode.