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SC18IM700

Master I2C-bus controller with UART interface

Philips Electronics 

Philips Semiconductors

SC18IM700

Master I2C-bus controller with UART interface

7. Functional description

The SC18IM700 is a bridge between a UART port and I2C-bus. The UART interface

consists of a full-functional advanced UART. The UART communicates with the host

through the TX and RX pins. The serial data format is fixed: one start bit, 8 data bits, and

one stop bit. After reset the baud rate defaults to 9600 bit/s, and can be changed through

the Baud Rate Generator (BRG) registers.

After a power-up sequence or a hardware reset, the SC18IM700 will send two continuous

bytes to the host to indicate a start-up condition. These two bytes are 0x4F and 0x4B;

‘OK’ in ASCII.

7.1 UART message format

The host initiates an I2C-bus data transfer, reads from and writes to SC18IM700 internal

registers through a series of ASCII commands. Table 3 lists the ASCII commands

supported by SC18IM700, and also their hexadecimal value representation.

Unrecognized commands are ignored by the device.

To prevent the host from handing the SC18IM700 due to an unfinished command

sequence, the SC18IM700 has a time-out feature. The delay between any two bytes of

data coming from the host should be less than 655 ms. If this condition is not met, the

SC18IM700 will time-out and clear the receive buffer. The SC18IM700 then starts to wait

for the next command from the host.

Table 3: ASCII commands supported by SC18IM700

ASCII command Hex value Command function

S

0x53

I2C-bus START

P

0x50

I2C-bus STOP

R

0x52

read SC18IM700 internal register

W

0x57

write to SC18IM700 internal register

I

0x49

read GPIO port

O

0x4F

write to GPIO port

Z

0x5A

power down

7.1.1 Write N bytes to slave device

The host issues the write command by sending an S character followed by an I2C-bus

slave device address, the total number of bytes to be sent, and I2C-bus data which begins

with the first byte (DATA 0) and ends with the last byte (DATA N). The frame is then

terminated with a P character. Once the host issues this command, the SC18IM700 will

access the I2C-bus slave device and start sending the I2C-bus data bytes.

Note that the second byte sent is the I2C-bus device slave address. The least significant

bit (W) of this byte must be set to 0 to indicate this is an I2C-bus write command.

SC18IM700_1

Product data sheet

Rev. 01 — 28 February 2006

© Koninklijke Philips Electronics N.V. 2006. All rights reserved.

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