eUSCI_B I2C Registers
847
SLAU367P – October 2012 – Revised April 2020
Copyright © 2012–2020, Texas Instruments Incorporated
Enhanced Universal Serial Communication Interface (eUSCI) – I
2
C Mode
32.4.2 UCBxCTLW1 Register
eUSCI_Bx Control Word Register 1
Figure 32-18. UCBxCTLW1 Register
15
14
13
12
11
10
9
8
Reserved
UCETXINT
r0
r0
r0
r0
r0
r0
r0
rw-0
7
6
5
4
3
2
1
0
UCCLTO
UCSTPNACK
UCSWACK
UCASTPx
UCGLITx
rw-0
rw-0
rw-0
rw-0
rw-0
rw-0
rw-0
rw-0
Can be modified only when UCSWRST = 1.
Table 32-5. UCBxCTLW1 Register Description
Bit
Field
Type
Reset
Description
15-9
Reserved
R
0h
Reserved
8
UCETXINT
RW
0h
Early UCTXIFG0. Only in slave mode. When this bit is set, the slave addresses
defined in UCxI2COA1 to UCxI2COA3 must be disabled.
Modify only when UCSWRST = 1.
0b = UCTXIFGx is set after an address match with UCxI2COAx and the direction
bit indicating slave transmit
1b = UCTXIFG0 is set for each START condition
7-6
UCCLTO
RW
0h
Clock low time-out select.
Modify only when UCSWRST = 1.
00b = Disable clock low time-out counter
01b = 135000 MODCLK cycles (approximately 28 ms)
10b = 150000 MODCLK cycles (approximately 31 ms)
11b = 165000 MODCLK cycles (approximately 34 ms)
5
UCSTPNACK
RW
0h
The UCSTPNACK bit allows to make the eUSCI_B master acknowledge the last
byte in master receiver mode as well. This does not conform to the I2C
specification and should only be used for slaves that automatically release the
SDA after a fixed packet length.
Modify only when UCSWRST = 1.
0b = Send a not acknowledge before the STOP condition as a master receiver
(conform to I2C standard)
1b = All bytes are acknowledged by the eUSCI_B when configured as master
receiver
4
UCSWACK
RW
0h
This bit selects whether sending an ACK of the address is triggered by the
eUSCI_B module or is controlled by software.
0b = The address acknowledge of the slave is controlled by the eUSCI_B
module
1b = The user needs to trigger the sending of the address ACK by issuing
UCTXACK
3-2
UCASTPx
RW
0h
Automatic STOP condition generation. In slave mode, only settings 00b and 01b
are available.
Modify only when UCSWRST = 1.
00b = No automatic STOP generation. The STOP condition is generated after
the user sets the UCTXSTP bit. The value in UCBxTBCNT is a don't care.
01b = UCBCNTIFG is set with the byte counter reaches the threshold defined in
UCBxTBCNT
10b = A STOP condition is generated automatically after the byte counter value
reached UCBxTBCNT. UCBCNTIFG is set with the byte counter reaching the
threshold.
11b = Reserved