UART/IrDA Control and Status Registers
12-74
Table 12–70 and Table 12–71 summarize the different ways that can be used
to set the trigger levels for the transmit FIFO and the receive FIFO, respectively.
Table 12–70. Transmit FIFO Trigger Level Setting Summary
SCR[6]
TLR[3:0]
TX FIFO Trigger Level
0
0000
Defined by FCR5:4 (either 8, 16, 32, and 56 spaces)
0
0
0000
Defined by TLR3:0 (from 4 to 60 spaces with a granularity of 4 spaces)
1
value
Defined by the concatenated value of TLR3:0 and FCR 5:4 (from 1 to 63
spaces with a granularity of 1 space).
The combination of TLR3:0 = 0000 and FCR 5:4 = 00 (all zeros) is not
supported (minimum one space required). All zeros result in unpredictable
behavior.
Note:
The protocol to set the concatenation of TLR and FCR is:
– Set SCR[6] = 0
– Set the value of threshold into FCR and TLR
– Set SCR[6] = 1
Table 12–71. Receive FIFO Trigger Level Setting Summary
SCR[7]
TLR[7:4]
TX FIFO Trigger Level
0
0000
Defined by FCR7:6 (either 8, 16, 56, and 60 characters)
0
0
0000
Defined by TLR7:4 (from 4 to 60 characters with a granularity of 4 characters)
1
value
Defined by the concatenated value of TLR7:4 and FCR 7:6 (from 1 to 63
characters with a granularity of 1 character).
The combination of TLR7:4 = 0000 and FCR 7:6 = 00 (all zeros) is not
supported (minimum one character required). All zeros result in unpredictable
behavior.
Note:
The protocol to set the concatenation of TLR and FCR is:
– Set SCR[7] = 0
– Set the value of threshold into FCR and TLR
– Set SCR[7] = 1