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.
SMSC DS – LPC47M192
Page 73
Rev. 03/30/05
DATASHEET
FIFO POLLED MODE OPERATION
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
75
110
134.5
150
300
600
1200
1800
2000
2400
3600
4800
7200
9600
19200
38400
57600
115200
230400
460800
DIVISOR USED TO
GENERATE 16X CLOCK
2304
1536
1047
857
768
384
192
96
64
58
48
32
24
16
12
6
3
2
1
32770
32769
PERCENT ERROR DIFFERENCE
BETWEEN DESIRED AND ACTUAL
1
0.001
-
-
0.004
-
-
-
-
-
0.005
-
-
-
-
-
-
0.030
0.16
0.16
0.16
0.16
HIGH
SPEED BIT
2
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
1
1
Note
1
: 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.
Table 31 - Reset Function Table
REGISTER/SIGNAL
RESET CONTROL
RESET STATE
Interrupt Enable Register
RESET
All bits low
Interrupt Identification Reg.
RESET
Bit 0 is high; Bits 1 - 7 low
FIFO Control
RESET
All bits low
Line Control Reg.
RESET
All bits low
MODEM Control Reg.
RESET
All bits low
Line Status Reg.
RESET
All bits low except 5, 6 high
MODEM Status Reg.
RESET
Bits 0 - 3 low; Bits 4 - 7 input