MCP3201

DS21290B-page 14

Preliminary

© 1999 Microchip Technology Inc.

5.0

SERIAL COMMUNICATIONS

Communication with the device is done using a stan-

dard SPI-compatible serial interface. Initiating commu-

nication with the MCP3201 begins with the CS going

low. If the device was powered up with the CS pin low,

it must be brought high and back low to initiate commu-

nication. The device will begin to sample the analog

input on the first rising edge after CS goes low. The

sample period will end in the falling edge of the second

clock, at which time the device will output a low null bit.

The next 12 clocks will output the result of the conver-

sion with MSB first, as shown in Figure 5-1. Data is

always output from the device on the falling edge of the

clock. If all 12 data bits have been transmitted and the

device continues to receive clocks while the CS is held

low, the device will output the conversion result LSB

first, as shown in Figure 5-2. If more clocks are pro-

vided to the device while CS is still low (after the LSB

first data has been transmitted), the device will clock

out zeros indefinitely.

FIGURE 5-1:

Communication with MCP3201 using MSB first Format.

FIGURE 5-2:

Communication with MCP3201 using LSB first Format.

CS

CLK

D

OUT

t

CYC

Power

Down

t

SUCS

t

SAMPLE

t

CONV

t

* After completing the data transfer, if further clocks are applied with CS low, the A/D Converter will output LSB first data, followed

by zeros indefinitely. See Figure below.

** t

node, leaving the CLK running to clock out the LSB-first data or zeros.

t

CSH

NULL

BIT

B11 B10 B9

B8

B7

B6

B5

B4

B3

B2

B1

HI-Z

HI-Z

NULL

BIT

B11 B10 B9

B8

CS

CLK

D

OUT

t

CYC

Power Down

t

SUCS

t

SAMPLE

t

CONV

t

* After completing the data transfer, if further clocks are applied with CS low, the A/D Converter will output zeros indefinitely.

** t

node, leaving the CLK running to clock out the LSB-first data or zeros.

t

CSH

NULL

BIT B11 B10

B9

B8

B7

B6

B5

B4

B3

B2

B1

B0

HI-Z

B1

B2

B3

B4

B5

B6

B7

B8

B9

B10

B11

*

HI-Z