455
32072H–AVR32–10/2012
AT32UC3A3
22.8.7
Identifying Bus Events
This chapter lists the different bus events, and how these affects the bits in the TWIS registers.
This is intended to help writing drivers for the TWIS.
Table 22-5.
Bus Events
Event
Effect
Slave transmitter has sent a
data byte
SR.THR is cleared.
SR.BTF is set.
The value of the ACK bit sent immediately after the data byte is given
by CR.ACK.
Slave receiver has received
a data byte
SR.RHR is set.
SR.BTF is set.
SR.NAK updated according to value of ACK bit received from master.
Start+Sadr on bus, but
address is to another slave
None.
Start+Sadr on bus, current
slave is addressed, but
address match enable bit in
CR is not set
None.
Start+Sadr on bus, current
slave is addressed,
corresponding address
match enable bit in CR set
Correct address match bit in SR is set.
SR.TRA updated according to transfer direction (updating is done one
CLK_TWIS cycle after address match bit is set)
Slave enters appropriate transfer direction mode and data transfer
can commence.
Start+Sadr on bus, current
slave is addressed,
corresponding address
match enable bit in CR set,
SR.STREN and SR.SOAM
are set.
Correct address match bit in SR is set.
SR.TRA updated according to transfer direction (updating is done one
CLK_TWIS cycle after address match bit is set).
Slave stretches TWCK immediately after transmitting the address
ACK bit. TWCK remains stretched until all address match bits in SR
have been cleared.
Slave enters appropriate transfer direction mode and data transfer
can commence.
Repeated Start received
after being addressed
SR.REP set.
SR.TCOMP unchanged.
Stop received after being
addressed
SR.STO set.
SR.TCOMP set.
Start, Repeated Start, or
Stop received in illegal
position on bus
SR.BUSERR set.
SR.STO and SR.TCOMP may or may not be set depending on the
exact position of an illegal stop.
Data is to be received in
slave receiver mode,
SR.STREN is set, and RHR
is full
TWCK is stretched until RHR has been read.
Data is to be transmitted in
slave receiver mode,
SR.STREN is set, and THR
is empty
TWCK is stretched until THR has been written.
Summary of Contents for AT32UC3A3128
Page 61: ...61 32072H AVR32 10 2012 AT32UC3A3 PLLEN PLL Enable 0 PLL is disabled 1 PLL is enabled...
Page 592: ...592 32072H AVR32 10 2012 AT32UC3A3 Manchester Configuration Register on page 614...
Page 989: ...989 32072H AVR32 10 2012 AT32UC3A3 37 2 Package Drawings Figure 37 1 TFBGA 144 package drawing...
Page 991: ...991 32072H AVR32 10 2012 AT32UC3A3 Figure 37 3 VFBGA 100 package drawing...