June 1989

6

Philips Semiconductors

Product specification

Infrared remote control transmitter RC-5

SAA3010

FUNCTIONAL DESCRIPTION

Keyboard operation

Every connection of one X-input and one DR-output will be recognized as a legal key operation and will cause the device

to generate the corresponding code. The same applies to every connection of one Z-input to one DR-output with the

proviso that SSM must be LOW. When SSM is HIGH a wired connection must exist between a Z-input and a DR-output.

If no connection is present the system number will not be generated. Activating two or more X-inputs, Z-inputs or Z-inputs

and X-inputs at the same time is an illegal action and inhibits further activity (oscillator will not start).

When one X- or Z-input is connected to more than one DR-output, the last scan signal will be considered as legal.

The maximum value of the contact series resistance of the switched keyboard is 7 k

Ω.

Inputs

In the quiescent state the command inputs X0 to X7 are held HIGH by an internal pull-up transistor. When the system

mode selection (SSM) input is LOW and the system is quiescent, the system inputs Z0 to Z3 are also held HIGH by an

internal pull-up transistor. When SSM is HIGH the pull-up transistor for the Z-inputs is switched off, in order to prevent

current flow, and a wired connection in the Z-DR matrix provides the system number.

Outputs

The output signal DATA transmits the generated information in accordance with the format illustrated by Fig.4 and

Tables 1 and 2. The code is transmitted using a biphase technique as illustrated by Fig.5. The code consists of four parts:

• Start part −1.5 bits (2 × logic 1)

• Control part −1 bit

• System part −5 bits

• Command part −6 bits

The output signal MDATA transmits the generated information modulated by 1/12 of the oscillator frequency with a 50%

duty factor.

In the quiescent state both DATA and MDATA are non-conducting (3-state outputs).

The scan driver outputs DR0 to DR7 are open drain n-channel transistors and conduct when the circuit is quiescent.

After a legal key operation the scanning cycle is started and the outputs switched to the conductive state one by one.

The DR-outputs were switched off at the end of the preceding debounce cycle.