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EPI Registers
1156
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
External Peripheral Interface (EPI)
16.5.17 EPIFIFOLVL Register (Offset = 0x200) [reset = 0x33]
EPI FIFO Level Selects (EPIFIFOLVL)
This register allows selection of the FIFO levels which trigger an interrupt to the interrupt controller or,
more efficiently, a DMA request to the µDMA. The NBRFIFO select triggers on fullness such that it
triggers on match or above (more full) in order for the processor or the µDMA to extract the read data. The
WFIFO triggers on emptiness such that it triggers on match or below (less entries) in order for the
processor or the µDMA to insert more write data.
It should be noted that the FIFO triggers are not identical to other such FIFOs in other peripherals. In
particular, empty and full triggers are provided to avoid wait states when using blocking operations.
The settings in this register are only meaningful if the µDMA is active or the interrupt is enabled.
Additionally, this register allows protection against writes stalling and notification of performing blocking
reads which stall for extra time due to preceding writes. The two functions behave in a non-orthogonal way
because read and write are not orthogonal.
The write error bit configures the system such that an attempted write to an already full WFIFO abandons
the write and signals an error interrupt to prevent accidental latencies due to stalling writes.
The read error bit configures the system such that after a read has been stalled due to any preceding
writes in the WFIFO, the error interrupt is generated. Note that the excess stall is not prevented, but an
interrupt is generated after the fact to notify that it has happened.
EPIFIFOLVL is shown in
and described in
.
Return to
Figure 16-46. EPIFIFOLVL Register
31
30
29
28
27
26
25
24
RESERVED
R-0x0
23
22
21
20
19
18
17
16
RESERVED
WFERR
RSERR
R-0x0
R/W-0x0
R/W-0x0
15
14
13
12
11
10
9
8
RESERVED
R-0x0
7
6
5
4
3
2
1
0
RESERVED
WRFIFO
RESERVED
RDFIFO
R-0x0
R/W-0x3
R-0x0
R/W-0x3
Table 16-30. EPIFIFOLVL Register Field Descriptions
Bit
Field
Type
Reset
Description
31-18
RESERVED
R
0x0
17
WFERR
R/W
0x0
Write Full Error
0x0 = The Write Full error interrupt is disabled. Writes are stalled
when the WFIFO is full until a space becomes available but an error
is not generated. Note that the Cortex-M4 write buffer may hide that
stall if no other memory transactions are attempted during that time.
0x1 = This bit enables the Write Full error interrupt (WTFULL in the
EPIEISC register) to be generated when a write is attempted and the
WFIFO is full. The write stalls until a WFIFO entry becomes
available.