SMB214C datasheet(22/26 Pages) SUMMIT

22 / 26 page

SMB214A/B/C

Summit Microelectronics, Inc

2128 2.0 6/20/2008

I2C PROGRAMMING INFORMATION

SERIAL INTERFACE

Access to the configuration registers, general-purpose

memory and command and status registers is carried

out over an industry standard 2-wire serial interface

2C). SDA is a bi-directional data line and SCL is a

clock input. Data is clocked in on the rising edge of

SCL and clocked out on the falling edge of SCL. All

data transfers begin with the MSB.

During data

transfers, SDA must remain stable while SCL is high.

Data is transferred in 8-bit packets with an intervening

clock period in which an Acknowledge is provided by

the device receiving data. The SCL high period (tHIGH)

is used for generating Start and Stop conditions that

precede and end most transactions on the serial bus.

A high-to-low transition of SDA while SCL is high is

considered a Start condition while a low-to-high

transition of SDA while SCL is high is considered a

Stop condition.

The interface protocol allows operation of multiple

devices and types of devices on a single bus through

unique device addressing.

The address byte is

comprised of a 7-bit device type identifier (slave

address). The remaining bit indicates either a read or

a write operation. Refer to Table 1 for a description of

the address bytes used by the SMB214A/B/C.

The device type identifier for the memory array, the

configuration registers and the command and status

registers are accessible with the same slave address.

The slave address can be can be programmed to any

seven bit number 0000000BIN through 1111111BIN.

WRITE

Writing to the memory or a configuration register is

illustrated in Figures 10 and 11. A Start condition

followed by the slave address byte is provided by the

host;

the

SMB214A/B/C

respond

with

Acknowledge; the host then responds by sending the

memory address pointer or configuration register

address pointer; the SMB214A/B/C respond with an

acknowledge; the host then clocks in one byte of data.

For memory and configuration register writes, up to 15

additional bytes of data can be clocked in by the host

to write to consecutive addresses within the same

page.

After the last byte is clocked in and the host receives

an Acknowledge, a Stop condition must be issued to

initiate the nonvolatile write operation.

READ

The address pointer for the non-volatile configuration

registers and memory registers as well as the volatile

command and status registers must be set before data

can be read from the SMB214A/B/C.

This is

accomplished by issuing a dummy write command,

which is a write command that is not followed by a

Stop condition. A dummy write command sets the

address from which data is read. After the dummy

write command is issued, a Start command followed

by the address byte is sent from the host. The host

then waits for an Acknowledge and then begins

clocking data out of the slave device. The first byte

read is data from the address pointer set during the

dummy write command.

Additional bytes can be

clocked out of consecutive addresses with the host

providing an Acknowledge after each byte. After the

data is read from the desired registers, the read

operation is terminated by the host holding SDA high

during the Acknowledge clock cycle and then issuing a

Stop condition. Refer to Figure 11 for an illustration of

the read sequence.

CONFIGURATION REGISTERS

The configuration registers are grouped with the

general-purpose memory.

GENERAL-PURPOSE MEMORY

The 96-byte general-purpose memory block is

segmented into two continuous independently lockable

blocks. The first 48-byte memory block begins at

block begins at the register address pointer C0HEX; see

Table 1. Each memory block can be locked

individually by writing to a dedicated register in the

configuration memory space.

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