TAS5508B clock control register

Ed Walker

The clock control register, address 0x00, does not appear to function as documented. Bit 0 is indicated as read only, to indicate if the clock setting is valid (I assume in comparison to the detected MCLK freq). Our goal is fs = 44.1 KHz with a 256 MCLK multiplier, so I am writing 0x4C to the register.

From the Bit 0 documentation, I would expect to read back 0x4D. Instead I read back 0x4C. If I write 0x4D to the register (with bit 0 set), then I do read back 0x4D.

over 13 years ago

0 Ed Walker over 13 years ago

Prodigy 5 points

Bit ‘0’ is meant to be used in manual clock mode as a clock valid bit.

In auto detect mode, no need to write 0x00. Device will auto detect the input clock.

In manual mode, user has to write ‘1’ and clock info to the LSB to let the device know clock settings are correct.

In your case, write 0x4D.

But if you are using auto detect, no need to write anything to this reg.

Most customers use the device in Autodetect mode. In that case, this bit is no more clock valid indicator.

So no need to write this bit. But I agree, “read only” is little confusing.

The data sheet should be updated to reflect this.

Audio

Audio forum

TAS5508B clock control register