Datasheet
2017 Microchip Technology Inc. DS60001516A-page 437
SAM9G20
30.7.6 TWI Status Register
Name: TWI_SR
Access: Read-only
TXCOMP: Transmission Completed (automatically set / reset)
TXCOMP used in Master mode
:
0: During the length of the current frame.
1: When both holding and shifter registers are empty and STOP condition has been sent.
TXCOMP behavior in Master mode can be seen in Figure 30-7 and in Figure 30-10.
TXCOMP used in Slave mode
:
0: As soon as a Start is detected.
1: After a Stop or a Repeated Start + an address different from SADR is detected.
TXCOMP behavior in Slave mode can be seen in Figure 30-27, Figure 30-28, Figure 30-29 and Figure 30-30.
RXRDY: Receive Holding Register Ready (automatically set / reset)
0: No character has been received since the last TWI_RHR read operation.
1: A byte has been received in the TWI_RHR since the last read.
RXRDY behavior in Master mode can be seen in Figure 30-10.
RXRDY behavior in Slave mode can be seen in Figure 30-25, Figure 30-28, Figure 30-29 and Figure 30-30.
TXRDY: Transmit Holding Register Ready (automatically set / reset)
TXRDY used in Master mode
:
0: The transmit holding register has not been transferred into shift register. Set to 0 when writing into TWI_THR.
1: As soon as a data byte is transferred from TWI_THR to internal shifter or if a NACK error is detected, TXRDY is set at the same time
as TXCOMP and NACK. TXRDY is also set when MSEN is set (enable TWI).
TXRDY behavior in Master mode can be seen in Figure 30-8.
TXRDY used in Slave mode
:
0: As soon as data is written in the TWI_THR, until this data has been transmitted and acknowledged (ACK or NACK).
1: It indicates that the TWI_THR is empty and that data has been transmitted and acknowledged.
If TXRDY is high and if a NACK has been detected, the transmission will be stopped. Thus when TRDY = NACK = 1, the programmer
must not fill TWI_THR to avoid losing it.
TXRDY behavior in Slave mode can be seen in Figure 30-24, Figure 30-27, Figure 30-29 and Figure 30-30.
31 30 29 28 27 26 25 24
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23 22 21 20 19 18 17 16
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15 14 13 12 11 10 9 8
TXBUFE RXBUFF ENDTX ENDRX EOSACC SCLWS ARBLST NACK
76543210
– OVRE GACC SVACC SVREAD TXRDY RXRDY TXCOMP