36) Philips RC-6 Protocol

RC-6 is, as may be expected, the successor of the RC-5 protocol. Like RC-5 the new RC-6 protocol was also defined by Philips. It is a very versatile and well defined protocol. Because of this versatility its original

definition

is many pages long. Here on

my page I will only summarize

the most important

properties of this protocol.

Features

Different modes of operation, depending on the intended use Dedicated Philips modes and OEM modes

Variable command length, depending on the operation mode Bi-phase coding (aka Manchester coding) Carrier frequency of 36kHz Manufacturer Philips

Modulation

RC-6 signals are modulated on a 36 between 25% and 50%.

Data is modulated using Manchester coding. This means that each bit (or symbol) will have both a mark and space in the output signal. If the symbol is a \half is a space. If the symbol is a \Please note that this is the opposite of the RC-5 protocol!

The main timing unit is 1t, which is 16 times the carrier period (1/36k * 16 = 444With RC-6 a total of 5 different symbols are defined:

s).

μ

kHz Infra Red carrier. The duty cycle of this carrier has to be

The leader pulse, which has a mark time of 6t (2.666ms) and a space time of 2t (0.889ms). This leader pulse is normally used to set the gain of the IR receiver unit.

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Normal bits, which have a mark time of 1t (0.444ms) and space time of 1t (0.444ms). A \and \

Trailer bits, which have a mark time of 2t (0.889ms) and a space time of 2t (0.889ms). Again a \

The leader and trailer symbols are only used in the header field of the messages, which will be explained in more detail below.

RC-6 Mode 0

I can only describe operation mode 0 because I have never actually seen other modes in use than the one my Philips TV understands. The way I understand it the other modes can vary extremely from mode 0.

Mode 0 is a dedicated Philips Consumer Electronics mode. It allows control of up to 256 independent devices, with a total of 256 commands per device.

The command is a concatenation of different information. I will cover these different components from left to right. Header field

The Header field consists of 3 different components.

First the leader symbol LS is transmitted. Its purpose is to adjust the gain of the IR receiving unit.

This leader symbol is followed by a start bit SB which always has the value \to calibrate the receiver's timing.

The mode bits mb2 ... mb0 determine the mode, which is 0 in this case, thus all three bits will be \

Finally the header is terminated by the trailer bit TR. Please note that the bit time of this symbol is twice as long as normal bits! This bit also serves as the traditional toggle bit, which will

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be inverted whenever a key is released. This allows the receiver to distinguish between a new key or a repeated key.

Control Field

This field holds 8 bits which are used as address byte. This means that a total of 256 different devices can be controlled using mode 0 of RC-6. The msb is transmitted first. Information Field

The information field holds 8 bits which are used as command byte. This means that each device can have up to 256 different commands. The msb is transmitted first. Signal Free Time

The Signal Free time is a period in which no data may be transmitted (by any device). It is important for the receiver to detect the signal free time at the end of a message to avoid incorrect reception. The signal free time is set to 6t, which is 2.666ms.

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37) Philips RC-5 Protocol

The RC-5 code from Philips is possibly the most used protocol by hobbyists, probably because of the wide availability of cheap remote controls. The protocol

is well

defined

for different

device

types

ensuring

compatibility

with

your

whole

entertainment system. Lately Philips started using a new protocol called RC-6 which has more features.

Features

5 bit address and 6 bit command length (7 command bits for RC5X) Bi-phase coding (aka Manchester coding) Carrier frequency of 36kHz

Constant bit time of 1.778ms (64 cycles of 36 kHz) Manufacturer Philips

Modulation

The protocol uses bi-phase modulation (or so-called Manchester coding) of a 36kHz IR carrier frequency. All bits are of equal length of 1.778ms in this protocol, with half of the bit time filled with a burst of the 36kHz carrier and the other half being idle. A logical zero is represented by a burst in the first half of the bit time. A logical one is represented by a burst in the second half of the bit time. The pulse/pause ratio of the 36kHz carrier frequency is 1/3 or 1/4 which reduces power consumption.

Protocol

The drawing below shows a typical pulse train of an RC-5 message. This example transmits command $35 to address $05.

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