Character timeout and RCVR FIFO trigger level interrupts have the same priority as the current received data available
interrupt; XMIT FIFO empty has the same priority as the current transmitter holding register empty interrupt.
6.5.5 FIFO POLLED MODE OPERTION
With FCR bit 0 = "1" resetting IER bits 0, 1, 2 or 3 or all to zero puts the UART in the FIFO Polled Mode of operation.
Since the RCVR and XMITTER are controlled separately, either one or both can be in the polled mode of operation.
In this mode, the user's program will check RCVR and XMITTER status via the LSR. LSR definitions for the FIFO
Polled.
Mode are as follows:
Bit 0=1 as long as there is one byte in the RCVR FIFO.
Bits 1 to 4 specify which error(s) have occurred. Character error status is handled the same way as when in the
interrupt mode, the IIR is not affected since EIR bit 2=0.
Bit 5 indicates when the XMIT FIFO is empty.
Bit 6 indicates that both the XMIT FIFO and shift register are empty.
Bit 7 indicates whether there are any errors in the RCVR FIFO.
There is no trigger level reached or timeout condition indicated in the FIFO Polled Mode, however, the RCVR and XMIT
FIFOs are still fully capable of holding characters.
Table 30 − Baud Rates
DESIRED
BAUD RATE
50
DIVISOR USED TO
GENERATE 16X CLOCK
PERCENT ERROR DIFFERENCE
HIGH
BETWEEN DESIRED AND ACTUAL1
SPEED BIT2
2304
1536
1047
857
768
384
192
96
0.001
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
1
75
-
110
-
134.5
150
0.004
-
300
-
600
-
1200
-
1800
64
-
2000
58
0.005
2400
48
-
3600
32
-
-
4800
24
7200
16
-
9600
12
-
19200
38400
57600
115200
230400
460800
6
-
3
0.030
0.16
0.16
0.16
0.16
2
1
32770
32769
1
Note1: The percentage error for all baud rates, except where indicated otherwise, is 0.2%.
Note 2: The High Speed bit is located in the Device Configuration Space.
SMSC DS – LPC47S45x
Page 71 of 259
Rev. 07/09/2001
DATASHEET
SMSC [ SMSC CORPORATION ]
