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.

+2.7V, Low-Power, Multichannel,

Serial 8-Bit ADCs

12

______________________________________________________________________________________

SSTRB

CS

SCLK

DIN

DOUT

14

8

12

16

20

24

START

SEL2 SEL1 SEL0

UNI/

BIP

SGL/

DIF

PD1

PD0

B7

B6

B5

B4

B3

B2

B1

B0

ACQUISITION

IDLE

FILLED WITH ZEROS

IDLE

CONVERSION

A/D STATE

RB1

RB2

RB3

4

µs

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