ATXMEGA32D4-CU View Datasheet(PDF) - Atmel Corporation
Part Name
Description
Manufacturer
ATXMEGA32D4-CU Datasheet PDF : 136 Pages
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8135L–AVR–06/12
XMEGA D4
Problem fix/Workaround
None.
22. TWI Transmit collision flag not cleared on repeated start
The TWI transmit collision flag should be automatically cleared on start and repeated start,
but is only cleared on start.
Problem fix/Workaround
Clear the flag in software after address interrupt.
23. Clearing TWI Stop Interrupt Flag may lock the bus
If software clears the STOP Interrupt Flag (APIF) on the same Peripheral Clock cycle as the
hardware sets this flag due to a new address received, CLKHOLD is not cleared and the
SCL line is not released. This will lock the bus.
Problem fix/Workaround
Check if the bus state is IDLE. If this is the case, it is safe to clear APIF. If the bus state is
not IDLE, wait for the SCL pin to be low before clearing APIF.
Code:
/* Only clear the interrupt flag if within a "safe zone". */
while ( /* Bus not IDLE: */
((COMMS_TWI.MASTER.STATUS & TWI_MASTER_BUSSTATE_gm) !=
TWI_MASTER_BUSSTATE_IDLE_gc)) &&
/* SCL not held by slave: */
!(COMMS_TWI.SLAVE.STATUS & TWI_SLAVE_CLKHOLD_bm)
)
{
/* Ensure that the SCL line is low */
if ( !(COMMS_PORT.IN & PIN1_bm) )
if ( !(COMMS_PORT.IN & PIN1_bm) )
break;
}
/* Check for an pending address match interrupt */
if ( !(COMMS_TWI.SLAVE.STATUS & TWI_SLAVE_CLKHOLD_bm) )
{
/* Safely clear interrupt flag */
COMMS_TWI.SLAVE.STATUS |= (uint8_t)TWI_SLAVE_APIF_bm;
}
24. TWI START condition at bus timeout will cause transaction to be dropped
If Bus Timeout is enabled and a timeout occurs on the same Peripheral Clock cycle as a
START is detected, the transaction will be dropped.
Problem fix/Workaround
None.
25. TWI Data Interrupt Flag erroneously read as set
When issuing the TWI slave response command CMD=0b11, it takes one Peripheral Clock
cycle to clear the data interrupt flag (DIF). A read of DIF directly after issuing the command
will show the DIF still set.
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