SPI Registers
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SPRUI07–March 2020
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Serial Peripheral Interface (SPI)
9.5.2.3 SPISTS Register (Offset = 2h) [reset = 0h]
SPISTS is shown in Figure 9-10 and described in Table 9-9.
Return to the Summary Table.
SPISTS contrains interrupt and status bits.
Figure 9-10. SPISTS Register
15 14 13 12 11 10 9 8
RESERVED
R-0h
7 6 5 4 3 2 1 0
OVERRUN_FL
AG
INT_FLAG BUFFULL_FLA
G
RESERVED
W1C-0h RC-0h R-0h R-0h
Table 9-9. SPISTS Register Field Descriptions
Bit Field Type Reset Description
15-8 RESERVED R 0h
Reserved
7 OVERRUN_FLAG W1C 0h
SPI Receiver Overrun Flag
This bit is a read/clear-only flag. The SPI hardware sets this bit when
a receive or transmit operation completes before the previous
character has been read from the buffer. The bit is cleared in one of
three ways:
- Writing a 1 to this bit
- Writing a 0 to SPI SW RESET (SPICCR.7)
- Resetting the system
If the OVERRUN INT ENA bit (SPICTL.4) is set, the SPI requests
only one interrupt upon the first occurrence of setting the RECEIVER
OVERRUN Flag bit. Subsequent overruns will not request additional
interrupts if this flag bit is already set. This means that in order to
allow new overrun interrupt requests the user must clear this flag bit
by writing a 1 to SPISTS.7 each time an overrun condition occurs. In
other words, if the RECEIVER OVERRUN Flag bit is left set (not
cleared) by the interrupt service routine, another overrun interrupt
will not be immediately re-entered when the interrupt service routine
is exited.
Reset type: SYSRSn
0h (R/W) = A receive overrun condition has not occurred.
1h (R/W) = The last received character has been overwritten and
therefore lost (when the SPIRXBUF was overwritten by the SPI
module before the previous character was read by the user
application).
Writing a '1' will clear this bit. The RECEIVER OVERRUN Flag bit
should be cleared during the interrupt service routine because the
RECEIVER OVERRUN Flag bit and SPI INT FLAG bit (SPISTS.6)
share the same interrupt vector. This will alleviate any possible
doubt as to the source of the interrupt when the next byte is
received.
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