Freescale Semiconductor MCF5480 User Manual
Page 960
MCF548x Reference Manual, Rev. 3
30-30
Freescale Semiconductor
30.3.3.21 FEC Receive FIFO Last Read Frame Pointer Register (FECRLRFP)
The last read frame pointer (LRFP) is a FIFO-maintained pointer that indicates the location of the next
byte after the last frame that has been completely read. If no frames have been read out of the FIFO, the
register indicates the first byte location in the FIFO(the reset state). The LRFP updates on FIFO read data
accesses to a frame boundary. The LRFP can be read and written for debug purposes. When
FECRFCR[FRMEN] is cleared, then this pointer has no meaning. The last read frame pointer is reset to
zero, and non-functional bits of this pointer will always remain zero.
30.3.3.22 FEC Receive FIFO Last Write Frame Pointer Register (FECRLWFP)
The last read frame pointer (LWFP) is a FIFO-maintained pointer that indicates the location of the next
byte after the last frame that has been completely written. If no frames have been written into the FIFO,
the register indicates the first byte location in the FIFO(the reset state). The LWFP updates on FIFO write
data accesses which create a frame boundary, whether that be by setting the WFR bit in the FIFO Control
Register, or by feeding a frame bit in on the appropriate bus. The LWFP can be read and written for debug
purposes. For the frame discard function, the LWFP divides the valid data region of the FIFO (the area
18-16
—
Reserved
15–0
COUNTER Timer mode counter. When the TIMER bit is set, the value of the COUNTER[15:0] bits are used to
determine the period of time that the frame ready request is suppressed. A request for service will
be made every (COUNTER[15:0] * 64) cycles as long as a valid frame exists in the FIFO.
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
R
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
W
Reset
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R
0
0
0
0
0
0
LRFP
W
Reset
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Reg
Addr
MBAR + 0x9190 (FEC0), 0x9990 (FEC1)
Figure 30-24. FEC Receive FIFO Last Read Frame Pointer Register (FECRLRFP)
Table 30-28. FECRLRFP Field Descriptions
Bits
Name
Descriptions
31–10
—
Reserved, should be cleared.
9–0
LRFP
Last read frame pointer. This pointer indicates the location of the next byte after the last frame that
has been completely read. If no frames have been read out of the FIFO, LRFP indicates the first
byte location in the FIFO( the reset state).
Table 30-27. FECRFCR Field Descriptions (Continued)
Bits
Name
Descriptions