Eusci_B Initialization And Reset - Texas Instruments MSP430x5 series User Manual

2
eUSCI_B Operation – I C Mode
Serial Data (SDA)
Serial Clock (SCL)
NOTE: SDA and SCL levels
The SDA and SCL pins must not be pulled up above the device V

41.3.1 eUSCI_B Initialization and Reset

The eUSCI_B is reset by a PUC or by setting the UCSWRST bit. After a PUC, the UCSWRST bit is
automatically set, keeping the eUSCI_B in a reset condition. To select I
must be set to 11b. After module initialization, it is ready for transmit or receive operation. Clear
UCSWRST to release the eUSCI_B for operation.
To avoid unpredictable behavior, configure or reconfigure the eUSCI_B module only when UCSWRST is
set. Setting UCSWRST in I
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• I C communication stops.
• SDA and SCL are high impedance.
• UCBxSTAT, bits 15-8 and 6-4 are cleared.
• Registers UCBxIE and UCBxIFG are cleared.
• All other bits and registers remain unchanged.
NOTE: Initializing or reconfiguring the eUSCI_B module
The recommended eUSCI_B initialization/reconfiguration process is:
1. Set UCSWRST (BIS.B
2. Initialize all eUSCI_B registers with UCSWRST = 1 (including UCxCTL1).
3. Configure ports.
4. Clear UCSWRST through software (BIC.B
5. Enable interrupts (optional).
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41.3.2 I C Serial Data
One clock pulse is generated by the master device for each data bit transferred. The I
with byte data. Data is transferred MSB first as shown in
The first byte after a START condition consists of a 7-bit slave address and the R/W bit. When R/W = 0,
the master transmits data to a slave. When R/W = 1, the master receives data from a slave. The ACK bit
is sent from the receiver after each byte on the ninth SCL clock.
1082
Enhanced Universal Serial Communication Interface (eUSCI) – I
V
CC
MSP430
2
Figure 41-2. I C Bus Connection Diagram
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C mode has the following effects:
#UCSWRST,&UCxCTL1).
#UCSWRST,&UCxCTL1).
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Copyright © 2008–2018, Texas Instruments Incorporated
Device A
Device B
level.
CC
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C operation, the UCMODEx bits
Figure 41-3.
SLAU208Q – June 2008 – Revised March 2018
C Mode
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Device C
2
C mode operates
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