TMS570LS1227 I2C ARDY Interrupt not thrown

Richard Derman2

I am working with a Microchip DAC MCP4728, which has a fairly simple I2C interface.

The interface is working well, but there is a troubling aspect to the operation that is making me uncomfortable. Although the ARDY interrupt is enabled, it is never generated. The operating mode is Master (Transmitter/Receiver), not Free Data Format. I have not needed to implement a repeat start for read operations.

In section 31.5.1.1/Table 31-2 of the Technical Reference Manual (SPNU515A) it says that the ARDY interrupt is generated "...when the previously programmed address, data, and command have been performed and the status bits have been updated."

Any insights into why I don't see this interrupt, or when it actually is generated would be greatly appreciated.

over 11 years ago

0 Chuck Davenport over 11 years ago

TI__Guru 59540 points

Hello Richard,

I have forwarded your question to our I2C IP expert. They are currently traveling and out of the office, but they should get back to you in a reasonable amount of time. If the issue is urgent and you need an answer immediately, let me know and I will escalate to another engineer.

0 Joe Josn over 11 years ago in reply to Chuck Davenport

Expert 1285 points

Hi Rick,

From the TRM: "When RM=0, ARDY is set when I2CCNT is passed 0 if STP register bit has not been set. When RM=1, ARDY is set at each byte end."

So in non-repeat mode, CNT register need to be set to > 0. ARDY will then be set when CNT register reaches 0 (Addr + all RX/TX completed) or on NAK?.

Hope it helps,

Joe

0 Richard Derman2 over 11 years ago in reply to Joe Josn

Intellectual 260 points

Thanks for looking into this. The key point that I had missed is that if STP is set, ARDY is not generated.

This helps a lot.

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TMS570LS1227 I2C ARDY Interrupt not thrown