Freescale Semiconductor MCF5480 - Manual (Page 794)

MCF548x Reference Manual, Rev. 3
26-32 Freescale Semiconductor
26.3.3.25 Rx and Tx FIFO Alarm Register (PSCRFARn, PSCTFARn)
26.3.3.26 Rx and Tx FIFO Read Pointer (PSCRFRPn, PSCTFRPn)
The read pointer is a FIFO-maintained pointer that points to the next FIFO location to be read. The physical
address of this FIFO location is actually the combination of the read pointer and the FIFO base, which is
21 RXW_MSK Receive wait condition mask. When this bit is set, the FIFO controller masks the status register’s
RXW bit from generating an error.
20 UF_MSK FIFO underflow mask. When this bit is set, the FIFO controller masks the status register’s UF bit
from generating an error.
19 OF_MSK FIFO overflow mask. When this bit is set, the FIFO controller masks the status register’s OF bit from
generating an error.
18 TXW_MSK Transmit wait condition mask. When this bit is set, the FIFO controller masks the status register’s
TXW bit from generating an error.
17-16 — Reserved, should be cleared.
15-0 CNTR Timer mode counter. When the TMR 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.
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
R 0 0 0 0 0 0 0
ALARM
W
Reset 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Reg
Addr
MBAR + 0x866E (PSCRFAR0); 0x876E (PSCRFAR1); 0x886E (PSCRFAR2); 0x896E (PSCRFAR3)
and MBAR + 0x868E (PSCTFAR0); 0x878E (PSCTFAR1); 0x888E (PSCTFAR2); 0x898E (PSCTFAR3)
Figure 26-22. RxFIFO (PSCRFARn) and TxFIFO (PSCTFARn) Alarm Register
Table 26-32. PSCRFARn and PSCTFARn Field Descriptions
Bits Name Description
15–9 — Reserved, should be cleared.
8–0 ALARM Alarm pointer
For Transmitter: The user writes these bits to set the low level “watermark”, which is the point at
which the FIFO asserts its request for data filling to the DMA controller. This value is in bytes. For
example, with ALARM = 32, the alarm condition will occur when the FIFO has 32 (or less) bytes in
it. The alarm, once asserted, will not negate until the high level mark is reached, as specified by the
granularity bits in the PSCTFCR.
For Receiver: The user writes these bits to set the high level “watermark”, which is the point at which
the FIFO asserts its request for data emptying to the DMA controller. This value is in bytes. For
example, with ALARM = 32, the alarm condition will occur when the FIFO has 32 (or more) bytes in
it. The alarm, once asserted will not negate until the low level mark is reached, as specified by the
granularity bits in the PSCRFCR.
Table 26-31. PSCRFCRn and PSCRTFCRn Field Descriptions (Continued)
Bits Name Description