UM10413
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© NXP B.V. 2011. All rights reserved.
User manual
Rev. 1 — 16 December 2011
85 of 268
NXP Semiconductors
UM10413
MPT612 User manual
[1]
Values "0000", “0011”, “0101”, “0111”, “1000”, “1001”, “1010”, “1011”,”1101”,”1110”,”1111” are reserved.
[2]
For details see
[3]
For details see
[4]
For details see
The UART0 THRE interrupt (U0IIR[3:1] = 001) is a third-level interrupt and is activated
when the UART0 THR FIFO is empty provided certain initialization conditions have been
met. These initialization conditions are intended to give the UART0 THR FIFO a chance to
fill up with data to eliminate many THRE interrupts from occurring at system start-up. The
initialization conditions implement a one-character delay minus the Stop bit whenever
THRE = 1 and there have not been at least two characters in the U0THR at one time since
the last THRE = 1 event. This delay is provided to give the CPU time to write data to
U0THR without a THRE interrupt to decode and service. If the UART0 THR FIFO has held
two or more characters at one time and currently, the U0THR is empty, a THRE interrupt
is set immediately. The THRE interrupt is reset when a U0THR write occurs or a read of
the U0IIR occurs and the THRE is the highest interrupt (U0IIR[3:1] = 001).
14.3.7 UART0 FIFO Control register (U0FCR - 0xE000 C008)
The U0FCR controls the operation of the UART0 Rx and Tx FIFOs.
0100
second
Rx data available
Rx data available or trigger level reached in FIFO
(U0FCR0 = 1)
U0RBR read
or
UART0 FIFO drops
below trigger level
1100
second
character time-out
indication
minimum of one character in Rx FIFO and no
character input or removed during a time period
depending on how many characters are in FIFO
and trigger level setting (3.5 to 4.5 character
times).
exact time is:
[(word length)
7
2]
8 + [(trigger level
number of characters)
8 + 1] RCLKs
U0RBR read
0010
third
THRE
THRE
U0IIR read (if source of
interrupt) or THR write
Table 91:
UART0 interrupt handling
…continued
U0IIR[3:0]
value
[1]
Priority
Interrupt type
Interrupt source
Interrupt reset