IR Sony SIRC Protocol Guide: Pulse Width Encoding & Decoding

Core Technical Specifications

center Freq 40 kHz infrared carrier

modulation Pulse Width Encoding

data Encoding 12-bit (7 cmd + 5 addr), 15-bit (7 cmd + 8 addr), 20-bit (7 cmd + 5 addr + 8 ext)

operating Range 5–10 m (line of sight)

antenna IR LED (940 nm) / TSOP4840 receiver

tx Power IR LED 20–100 mA peak

bandwidth 40 kHz ±2 kHz

channel Spacing N/A

Real-World Devices & Applications

Sony Consumer Electronics

Sony TVs (Bravia series)
PlayStation consoles (PS3/PS4/PS5 remote)
Sony Blu-ray and DVD players
Sony soundbars and audio systems
Sony cameras with IR remote capability

Reference Circuits & Schematics

SIRC IR Receiver — TSOP4840

The TSOP4840 is optimised for 40 kHz — the specific carrier frequency used by Sony SIRC. Using a 38 kHz receiver will work but with reduced range.

Pin	Description
`VOUT`	Demodulated output (active LOW)
`GND`	Ground
`VCC`	2.5–5.5V supply

Circuit Walk-Through

SIRC pulse width encoding: a 600 µs burst followed by 600 µs space = logic 0; a 1200 µs burst followed by 600 µs space = logic 1. The 2.4 ms leader pulse + 600 µs gap starts each frame. Command is sent 3 times minimum (Sony spec requires receiver to validate 3 identical frames before acting).

Signal Structure & Waveform Analysis

SIRC 12-Bit Frame Structure

SIRC encodes bits using variable-width carrier bursts. The leader pulse is distinctive at 2.4 ms.

Leader

Start mark

2.4 ms burst + 600 µs space

Command

7 bits (LSB first)

600 µs burst = '0', 1200 µs burst = '1', 600 µs gap between

Address

5 bits (12-bit) or 8 bits (15-bit)

Same pulse width encoding

Extended

8 bits (20-bit only)

Additional device sub-address

Timing Notes: Frame period: 45 ms (start of one frame to start of next). Command sent minimum 3 times. Total burst for a button press: ~135 ms minimum. 15-bit and 20-bit variants extend address space for more Sony device types.

Analysis & Capture Tips

Note 40 kHz carrier — not 38 kHz. Use TSOP4840 for best results
SIRC sends LSB first (opposite to NEC which also sends LSB first but different timing)
Three identical frames required for valid decode — check all 3 match
Use IRremote library with DECODE_SONY enabled

Bench Troubleshooting & Repair Guide

1. 40 kHz Carrier

Oscilloscope

Sony uses 40 kHz, not 38 kHz. A 38 kHz receiver works but with ∼30% reduced range. For repair, replace with TSOP4840.

2. Triple-Send Requirement

Logic Analyser / IR capture

Sony receivers require 3 identical frames. If the remote’s battery is weak, the third frame may differ (frequency drift), causing intermittent failures.

3. Protocol Version

IRremote debug output

Identify whether the device uses 12, 15, or 20-bit SIRC. Sending wrong bit count = wrong address decode. Check Sony service manual for model-specific protocol.

IR Sony SIRC