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M0A21/M0A23 Series
May 06, 2022
Page
487
of 746
Rev 1.02
M0
A21
/M
0
A
2
3
SE
RIES
TEC
H
NICAL
RE
FEREN
C
E
M
ANUAL
Data Shift Unit
Digital
Filter
0
1
Protocol Processor
Unit
IN_SYNC
SYNCSEL
(USCI_CLKIN[0])
USCIx_CLK
Figure 6.12-3 Input Conditioning for USCIx_CLK
All configurations of control, clock and data input structures are in USCI_CTLIN0, USCI_CLKIN and
USCI_DATIN0 registers respectively. EDGEDET (USCI_DATIN0[4:3]) is used to select the edge
detection condition. Note that the EDGEDET for USCI_DATIN0 must be s
et 2’b10 in UART mode. The
programmable edge detection indicates that the desired event has occurred by activating the trigger
signal.
ININV (USCI_DATIN0[2] / USCI_CTLIN0[2]) allows a polarity inversion of the selected input signal to
adapt the input signal polarity to the internal polarity of the data shift unit and the protocol state machine.
If the SYNCSEL (USCI_DATIN0[0] / USCI_CTLIN0[0] / USCI_CLKIN[0]) is set to 0, the paths of input
signals do not contain any delay due to synchronization or filtering. If there is noise on the input signals,
there is the possibility to synchronize the input signal (signal IN_SYNC is synchronized to
f
PCLK
). The
synchronized input signal is taken into account by SYNCSEL = 1. The synchronization leads to a delay
in the signal path of 2-3 times the period of
f
PCLK
.
Output Signals
Table 6.12-2 shows the relative output signals for each protocol. The number of actually used outputs
depends on the selected protocol and they can be classified according to their meaning for the protocols.
Selected Protocol
UART
SPI
I
2
C
Serial Bus
Clock Output
USCIx_CLK
-
SPI_CLK
SCL
Control Output
USCIx_CTL0
-
SPI_SS
-
USCIx_CTL1
nRTS
-
-
Data Output
USCIx_DAT0
-
SPI_MOSI_0
SDA
USCIx_DAT1
TX
SPI_MISO_0
-
Table 6.12-2 Output Signals for Different Protocols
The description of protocol-specific items are given in the related protocol chapters.
6.12.4.2 Data Buffering
The data handling of the USCI controller is based on a Data Shift Unit (DSU) and a buffer structure.