Deserial Serial Peripheral Interface (DSPI)
MPC5510 Microcontroller Family Reference Manual, Rev. 1
23-60
Freescale Semiconductor
Preliminary
23.5.4
Calculation of FIFO Pointer Addresses
The user has complete visibility of the TX and RX FIFO contents through the FIFO registers, and valid
entries can be identified through a memory-mapped pointer and a memory-mapped counter for each FIFO.
The pointer to the first-in entry in each FIFO is memory mapped. For the TX FIFO the first-in pointer is
the transmit next pointer (TXNXTPTR). For the RX FIFO the first-in pointer is the pop next pointer
(POPNXTPTR).
illustrates the concept of first-in and last-in FIFO entries along with the
FIFO counter. The TX FIFO is chosen for the illustration, but the concepts carry over to the RX FIFO. See
Section 23.4.3.4, “Transmit First-In First-Out (TX FIFO) Buffering Mechanism
“Receive First-In First-Out (RX FIFO) Buffering Mechanism
,” for details on the FIFO operation.
Table 23-31. Delay Values
Delay Prescaler Values
(DSPI_CTAR[PBR])
1
3
5
7
De
la
y Sc
aler
V
a
lues
(DSPI_CT
A
R[DT])
2
30.0 ns
90.0 ns
150.0 ns
210.0 ns
4
60.0 ns
180.0 ns
300.0 ns
420.0 ns
8
120.0 ns
360.0 ns
600.0 ns
840.0 ns
16
240.0 ns
720.0 ns
1.2
μ
s
1.65
μ
s
32
480.0 ns
1.44
μ
ns
2.4
μ
s
3.3
μ
s
64
960.0 ns
2.9
μ
s
4.8
μ
s
6.8
μ
s
128
2.0
μ
s
5.7
μ
s
9.6
μ
s
13.5
μ
s
256
3.9
μ
s
11.6
μ
s
19.2
μ
s
26.9
μ
s
512
7.7
μ
s
23.1
μ
s
38.4
μ
s
53.7
μ
s
1024
15.3
μ
s
46.1
μ
s
76.8
μ
s
107.6
μ
s
2048
30.8
μ
s
92.1
μ
s
153.6
μ
s
215.1
μ
s
4096
61.6
μ
s
184.4
μ
s
307.2
μ
s
430.1
μ
s
8192
122.9
μ
s
368.7
μ
s
614.4
μ
s
860.1
μ
s
16384
245.7
μ
s
737.3
μ
s
1.2 ms
1.7 ms
32768
491.6
μ
s
1.5 ms
2.4 ms
3.5 ms
65536
998.1
μ
s
2.0 ms
3.0 ms
6.9 ms