EM3027

Copyright

 2013, EM Microelectronic-Marin SA

3027-DS.doc, Version 8.0, 25-Jan-13

13

www.emmicroelectronic.com

Figure 2: I2C Communication

Noise suppression circuitry is implemented rejecting spikes shorter than 50ns on SCL and SDA bus lines.

7.2

How to perform data transmission through SPI

The SPI interface connects master and slave circuits.

4 connections are used: CS = Chip Select, SCK = Serial

Clock, SI = Serial Data Input and SO = Serial Data

Output.

SPI is a byte oriented protocol with MSB first mode. Data

are changing on SCK falling edge and sampled on rising

edge.

A transmission is started by the master by rising the CS

input of the selected slave to ‘1’. The transmission is

terminated by the master by putting ‘0’ level the CS input.

The first bit is the R/W bit,

R/W = ‘0’ means a WRITE

transmission, where the master sends the data via the SI

line

. R/W = ‘1’ defines a READ transmission, where the

slave outputs the data on the SO line.

The following 7 bits of the first byte form the address of

the register in the EM3027, where the data are written or

read. (MSB is first bit at position 2 in this address byte.)

The not transmitted 8

internally to ‘0’.

In the EM3027, the upper 5 bits of an address form a

“page address”, the 3 lower bits are an auto-incrementing

sub-address. The

“page-addres’’ is defined by a WRITE

transmission. During a transmission, the 3 lower address

bits are incremented internally after each byte.

During a WRITE transmission, the master defines the

register address and sends then data bytes, using the

auto-increment of the lower address part (bit 2 to 0)

within the EM3027.

The page address is fixed until a new transmission is

started.

SO data output of EM3027 is in Hi-Z state during the

WRITE transmission.

If READ transmission is initiated, data are output after

the address byte by the EM3027.

The lower part of the address (bit 2 to 0) is automatically

incremented after each data byte. The page address is

not changed until a new transmission is started.

SO is in Hi-Z while the address byte is sent. During data

output by SO, the SI input has no influence.

When CS is at ‘0’ level, SO is Hi-Z and SCK, SI can be

left floating.

SO and SI can be connected together to form a 3-wire

interface with CS, SCK and Serial Data Input/Output.

The EM3027 works as slave. The CS input has a pull-

down resistor of 100 kΩ.

1

2

9

8

7

6

SCL

1

2

8

7

6

9

Start Condition

Stop Condition

A6

A5

ACK

SDA

R/W

A1

A0

D7

D6

ACK

D0

D2

D1

Slave Address

Data Byte, send/receive as

many as needed

Read/Write selection bit