Rainbow Electronics MAX1111 - Manual (Page 12)

Simple Software Interface
Make sure the CPU’s serial interface runs in master
mode so the CPU generates the serial clock. Choose a
clock frequency from 50kHz to 500kHz.
1) Set up the control byte for external clock mode and
call it TB1. TB1 should be of the format 1XXXXX11
binary, where the Xs denote the particular channel
and conversion mode selected.
2) Use a general-purpose I/O line on the CPU to pull
CS low.
3) Transmit TB1 and, simultaneously, receive a byte
and call it RB1. Ignore RB1.
4) Transmit a byte of all zeros ($00 hex) and, simulta-
neously, receive byte RB2.
5) Transmit a byte of all zeros ($00 hex) and, simulta-
neously, receive byte RB3.
6) Pull CS high.
Figure 7 shows the timing for this sequence. Bytes RB2
and RB3 contain the result of the conversion padded
with two leading zeros and six trailing zeros. The total
conversion time is a function of the serial-clock
frequency and the amount of idle time between 8-bit
transfers. Make sure that the total conversion time does
not exceed 1ms, to avoid excessive T/H droop.
Digital Inputs
CS, SCLK, and DIN can accept input signals up to
5.5V, regardless of the supply voltages. This allows the
MAX1110/MAX1111 to accept digital inputs from both
3V and 5V systems.
MAX1110/MAX1111
+2.7V, Low-Power, Multichannel,
Serial 8-Bit ADCs
12 ______________________________________________________________________________________
SSTRB
CS
SCLK
DIN
DOUT
1 4 8 12 16 20 24
START
SEL2 SEL1 SEL0
UNI/
BIP
SGL/
DIF
PD1 PD0
B7 B6 B5 B4 B3 B2 B1 B0
ACQUISITION
(f SCLK = 500kHz)
IDLE
FILLED WITH ZEROS
IDLE CONVERSION
t
ACQ
A/D STATE
RB1 RB2 RB3
4 µ s
Figure 7. Single-Conversion Timing, External Clock Mode, 24 Clocks
CS
SCLK
DOUT
I/O
SCK
MISO
+3V
SS
a) SPI
CS
SCLK
DOUT
CS
SCK
MISO
+3V
SS
b) QSPI
MAX1110
MAX1111
MAX1110
MAX1111
MAX1110
MAX1111
CS
SCLK
DOUT
I/O
SK
SI
c) MICROWIRE
Figure 6. Common Serial-Interface Connections to the
MAX1110/MAX1111