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M0A21/M0A23 Series
May 06, 2022
Page
565
of 746
Rev 1.02
M0
A21
/M
0
A
2
3
SE
RIES
TEC
H
NICAL
RE
FEREN
C
E
M
ANUAL
USCI Protocol Status Register
– USPI_PROTSTS (SPI)
Register
Offset
R/W
Description
Reset Value
USPI_PROTSTS
U0x64
R/W
USCI Protocol Status Register
0x0000_0000
31
30
29
28
27
26
25
24
Reserved
23
22
21
20
19
18
17
16
Reserved
SLVUDR
BUSY
SSLINE
15
14
13
12
11
10
9
8
Reserved
SSACTIF
SSINAIF
7
6
5
4
3
2
1
0
Reserved
SLVBEIF
SLVTOIF
RXENDIF
RXSTIF
TXENDIF
TXSTIF
Reserved
Bits
Description
[31:19]
Reserved
Reserved.
[18]
SLVUDR
Slave Mode Transmit Under-run Status (Read Only)
In Slave mode, if there is no available transmit data in buffer while transmit data shift out caused by input serial
bus clock, this status flag will be set to 1. This bit indicates whether the current shift-out data of word
transmission is switched to TXUDRPOL (USPI_PROTCTL[28]) or not.
0 = Slave transmit under run event does not occur.
1 = Slave transmit under run event occurs.
[17]
BUSY
Busy Status (Read Only)
0 = SPI is in idle state.
1 = SPI is in busy state.
The following listing are the bus busy conditions:
a.
USPI_PROTCTL[31] = 1 and the TXEMPTY = 0.
b.
For SPI Master mode, the TXEMPTY = 1 but the current transaction is not finished yet.
c.
For SPI Slave mode, the USPI_PROTCTL[31] = 1 and there is serial clock input into the SPI core
logic when slave select is active.
d.
For SPI Slave mode, the USPI_PROTCTL[31] = 1 and the transmit buffer or transmit shift register
is not empty even if the slave select is inactive.
[16]
SSLINE
Slave Select Line Bus Status (Read Only)
This bit is only available in Slave mode. It used to monitor the current status of the input slave select signal on
the bus.
0 = The slave select line status is 0.
1 = The slave select line status is 1.
[15:10]
Reserved
Reserved.
[9]
SSACTIF
Slave Select Active Interrupt Flag
This bit indicates that the internal slave select signal has changed to active. It is cleared by software writes
one to this bit
0 = The slave select signal has not changed to active.
1 = The slave select signal has changed to active.
Note:
The internal slave select signal is active high.