Texas Instruments manual 6.3.2TAS3002 I2C Readback Example, 6.3.3I2C Wait States

6.3.2TAS3002 I2C Readback Example

The TAS3002 saves in a stack or first-in first-out (FIFO) buffer the last 7 bytes that were sent to it. When an I2C read command is sent to the device (LSB=high), it answers by popping the first byte off the stack. The TAS3002 then expects either a Send Ack command or an I2C Stop command from the host. If a Send Ack command is sent from the host then the TAS3002 pops another byte off the stack. If an I2C Stop is sent then the TAS3002 ends this transaction. The proper sequence for reading is described as follows:

I2C Start

Send I2C address byte with read bit set to 1 (LSB set equal to 1)

Receive Byte 0

Send Ack

Receive Byte 1

Send Ack

Receive Byte 2

Send Ack

Receive Byte 3

Send Ack

Receive Byte 4

Send Ack

Receive Byte 5

Send Ack

Receive Byte 6 (if an ACK is sent after byte 6 it locks up the TAS3002)

I2C Stop

Where:

•I2C Start is a valid I2C Start command.

•Receive Byte is a valid I2C command which reads a byte from the TAS3002.

•Send Ack is a a valid I2C command that informs the TAS3002 that a byte has been read.

•I2C Stop is a valid I2C Stop command.

NOTES: 1. The TAS3002 will appear to be locked up, if a Send Ack is issued after the last byte read. It is required to send an I2C Stop command after the last byte and not a Send Ack.

2.The I2C Start and I2C Stop commands are the same for both I2C read and I2C write.

6.3.3I2C Wait States

The TAS3002 device performs interpolation algorithms for its volume and tone controls. If a volume or tone change is sent to the part via I2C, the command sent after the volume or tone (bass and treble) change causes an I2C wait state to occur. This wait state lasts from 41 ms to 231 ms, depending on the system clock rate, the command sent, and, in the case of bass or treble, the amount of the change.

Secondly, if a long series of commands is sent to the TAS3002 device, it may occasionally create a short wait state on the order of 150 ∝s to 300 ∝s while it loads and processes the commands.

When a sample rate of 32 kHz is used, longer wait states can occur, occasionally up to 15 ms.

The preferred way to take care of wait states is to use an I2C controller that recognizes wait states. During the wait state period, it stops sending data over I2C. If this function is not available on the system controller, fixed delays can be implemented in the system software to ensure that the controller is not trying to send more data while the TAS3002 device is busy. Sending I2C data while the TAS3002 device is busy causes errors and locks up the device, which must then be reset.

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