cx29503 Mindspeed Technologies, cx29503 Datasheet - Page 211

• Manufacturer Part Number: cx29503
• Description: Cx29503 Broadband Access Multiplexer Data Sheet
• Manufacturer: Mindspeed Technologies

CX29503 Data Sheet
0xAB—TDL 1 FIFO Empty Control (TDL1_FEC)
Unused bits are reserved and should be written to 0.
FEC[5:0]
29503-DSH-002-B
—
7
Near-Empty Transmit FIFO Threshold—Selects the FIFO depth of the near-empty interrupt
[TNEAR; addr: 009] and near-empty level status [TNEAR1; addr: 0AE]. The TNEAR
interrupt is activated when the number of data bytes remaining to be transmitted from the FIFO
falls below the selected threshold, see
the number of processor-filled FIFO locations is below the selected threshold. TNEAR1 is
active-high when the transmit FIFO is completely empty and remains active until the processor
writes the selected threshold number of bytes to TDL1 [addr: 0AD].
Assuming the processor writes 64 bytes to completely fill an empty FIFO, then a TNEAR
interrupt occurs after the transmitter has sent the number of bytes required to bring the FIFO
level back down below the selected threshold. Hence, the processor can consecutively write
64–FEC[5:0] number of bytes to the transmit FIFO in response to a TNEAR interrupt. The
interrupt also signifies how much time remains (in bytes) for the processor to write TDL1
before the transmit FIFO is emptied. Typically, FEC[5:0] is set to a small value (below the 10-
byte threshold) to minimize the number of TNEAR interrupts and maximize the time between
TNEAR interrupts.
—
6
Table 8-37. TNEAR Interrupt Threshold
00 0000
00 0001
00 0010
11 1110
11 1111
FEC[5:0]
FEC[5]
—
5
.
.
.
Mindspeed Technologies™
Disabled
1 byte threshold
2 byte threshold
62 byte threshold
63 byte threshold
FEC[4]
Preliminary Information
4
Byte threshold at TNEAR
Table
FEC[3]
8-37. The TNEAR1 indicator is active as long as
3
—
.
.
.
FEC[2]
2
Disabled
63 empty
62 empty
2 empty
1 empty
FEC[1]
1
Empty at TNEAR
Register Description
—
.
.
.
FEC[0]
0
8
-
81