IDT I2C Bus Interface
I2C Bus Slave Interface
79RC32438 User Reference Manual
15 - 15
November 4, 2002
Notes
I
2
C Bus Slave Status Mask Register
Figure 15.18 I
2
C Bus Slave Status Mask Register (I2CSSM)
SA
Description:
Slave Addressed.
This bit is set when the slave interface determines that it has been addressed
by an I
2
C bus master. This occurs when an address on the I
2
C bus matches that in the
I2CSADDR register, or when the general call address (zero) is observed and the GCE bit is set
in the I2CSADDR register. Clearing this bit causes the slave interface to release the I
2
C bus.
Initial Value:
Undefined
Read Value:
Status
Write Effect:
Clear to release I
2
C bus
TF
Description:
Transaction Finished.
This bit is set when the slave interface determines that it is no longer
addressed by an I
2
C bus master. This occurs as the result of a stop or repeated start condition.
Initial Value:
Undefined
Read Value:
Status
Write Effect:
Clear to release I
2
C bus
GC
Description:
General Call.
This bit is set when the slave interface observes a general call address on the I
2
C
bus and the GCE bit in the I2CSADDR register is set.
Initial Value:
Undefined
Read Value:
Status
Write Effect:
Sticky bit (a sticky bit is set by the hardware and can only be cleared by the CPU)
NA
Description:
No Acknowledge.
This bit reflects the state of the acknowledgment signal driven during the pre-
vious I
2
C bus acknowledge phase in which the slave interface was addressed (that is, it reflects
the value of the ACK on the wire).
Initial Value:
Undefined
Read Value:
Status
Write Effect:
Sticky bit (a sticky bit is set by the hardware and can only be cleared by the CPU)
ERR
Description:
Error.
This bit is set when a start or stop condition is detected in an illegal position during a I
2
C
bus transaction in which the slave interface is addressed.
Initial Value:
Undefined
Read Value:
Status
Write Effect:
Sticky bit (a sticky bit is set by the hardware and can only be cleared by the CPU)
I2CSSM
0
31
RR
0
25
1
WR
1
TF
1
NA
1
ERR
1
SA
1
GC
1