LM3S5791_16 Datasheet, PDF (511/1336 Pages) Texas Instruments – Stellaris LM3S5791 Microcontroller

Stellaris^® LM3S5791 Microcontroller
Register 15: EPI Non-Blocking Read Data 0 (EPIRPSTD0), offset 0x028
Register 16: EPI Non-Blocking Read Data 1 (EPIRPSTD1), offset 0x038
This register sets up a non-blocking read via the external interface. A non-blocking read is started
by writing to this register with the count (other than 0). Clearing this register terminates an active
non-blocking read as well as cancelling any that are pending. This register should always be cleared
before writing a value other than 0; failure to do so can cause improper operation. Note that both
NBR channels can be enabled at the same time, but NBR channel 0 has the highest priority and
channel 1 does not start until channel 0 is finished.
The first address is based on the corresponding EPIRADDRn register. The address register is
incremented by the size specified by the EPIRSIZEn register after each read. If the size is less than
a word, only the least significant bits of data are filled into the NBRFIFO; the most significant bits
are cleared.
Note that all three registers may be written using one STM instruction, such as with a structure copy
in C/C++.
The data may be read from the EPIREADFIFO register after the read cycle is completed. The
interrupt mechanism is normally used to trigger the FIFO reads via ISR or μDMA.
If the countdown has not reached 0 and the NBRFIFO is full, the external interface waits until a
NBRFIFO entry becomes available to continue.
Note: if a blocking read or write is performed through the address mapped area (at 0x6000.0000
through 0xDFFF.FFFF), any current non-blocking read is paused (at the next safe boundary), and
the blocking request is inserted. After completion of any blocking reads or writes, the non-blocking
reads continue from where they were paused.
The other way to read data is via the address mapped locations (see the EPIADDRMAP register),
but this method is blocking (core or μDMA waits until result is returned).
To cancel a non-blocking read, clear this register. To make sure that all values read are drained
from the NBRFIFO, the EPISTAT register must be consulted to be certain that bits NBRBUSY and
ACTIVE are cleared. One of these registers should not be cleared until either the other EPIRPSTDn
register becomes active or the external interface is not busy. At that point, the corresponding
EPIRADDRn register indicates how many values were read.
EPI Non-Blocking Read Data 0 (EPIRPSTD0)
Base 0x400D.0000
Offset 0x028
Type R/W, reset 0x0000.0000
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
reserved
Type RO
RO
RO
RO
RO
RO
RO
RO
RO
RO
RO
RO
RO
RO
RO
RO
Reset
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
15
14
13
reserved
Type RO
RO
RO
Reset
0
0
0
12
11
10
9
8
7
6
5
4
3
2
1
0
POSTCNT
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
0
0
0
0
0
Bit/Field
31:13
Name
reserved
Type
RO
Reset Description
0x0000.0
Software should not rely on the value of a reserved bit. To provide
compatibility with future products, the value of a reserved bit should be
preserved across a read-modify-write operation.
July 03, 2014
511
Texas Instruments-Production Data