TX FIFO Max
Level
Progammable
Threshold
(TXTRSH)
Zero Byte
TXTRSH
XRDY Condition
(Active Low)
Time
Time
RX FIFO Max
Level
Progammable
Threshold
(RXTRSH)
Zero Byte
RXTRSH
RRDY Condition
(Active Low)
Functional Description
Figure 21-11. Receive FIFO Interrupt Request Generation
Note that in
, the RRDY Condition illustrates that the condition for generating a RRDY
interrupt is achieved. The interrupt request is generated when this signal is active, and it can be cleared
only by the CPU by writing a 1 in the corresponding interrupt flag. If the condition is still present after
clearing the previous interrupt, another interrupt request will be generated.
In receive mode, RRDY interrupt is not generated until the FIFO reaches its receive threshold. Once low,
the interrupt can only be de-asserted when the Local Host has handled enough bytes to make the FIFO
level below threshold. For each interrupt, the Local Host can be configured to read an amount of bytes
equal with the value of the RX FIFO thr 1.
Figure 21-12. Transmit FIFO Interrupt Request Generation
Note that in the figure above, the XRDY Condition illustrates that the condition for generating a XRDY
interrupt is achieved. The interrupt request is generated when this condition is achieved (when TX FIFO is
empty, or the TX FIFO threshold is not reached and there are still data bytes to be transferred in the TX
FIFO), and it can be cleared only by the CPU by writing a 1 in the corresponding interrupt flag after
transmitting the configured number of bytes. If the condition is still present after clearing the previous
interrupt, another interrupt request will be generated.
Note that in interrupt mode, the module offers two options for the CPU application to handle the interrupts:
•
When detecting an interrupt request (XRDY or RRDY type), the CPU can write/read one data byte
to/from the FIFO and then clear the interrupt. The module will not reassert the interrupt until the
3710
I2C
SPRUH73H – October 2011 – Revised April 2013
Copyright © 2011–2013, Texas Instruments Incorporated