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UM10375
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© NXP B.V. 2011. All rights reserved.
User manual
Rev. 3 — 14 June 2011
197 of 368
NXP Semiconductors
UM10375
Chapter 12: LPC13xx UART
4. During the receipt of the start bit (and the character LSB for Mode = 0), the rate
counter will continue incrementing with the pre-scaled UART input clock
(UART_PCLK).
5. If Mode = 0, the rate counter will stop on next falling edge of the UART Rx pin. If
Mode = 1, the rate counter will stop on the next rising edge of the UART Rx pin.
6. The rate counter is loaded into U0DLM/U0DLL and the baud rate will be switched to
normal operation. After setting the U0DLM/U0DLL, the end of auto-baud interrupt
U0IIR ABEOInt will be set, if enabled. The U0RSR will now continue receiving the
remaining bits of the ”A/a" character.
a. Mode 0 (start bit and LSB are used for auto-baud)
b. Mode 1 (only start bit is used for auto-baud)
Fig 22. Auto-baud a) mode 0 and b) mode 1 waveform
UARTn RX
start bit
LSB of 'A' or 'a'
U0ACR start
rate counter
start
bit0
bit1
bit2
bit3
bit4
bit5
bit6
bit7
parity stop
'A' (0x41) or 'a' (0x61)
16 cycles
16 cycles
16xbaud_rate
UARTn RX
start bit
LSB of ©A© or ©a©
rate counter
©A© (0x41) or ©a© (0x61)
start
bit0
bit1
bit2
bit3
bit4
bit5
bit6
bit7
parity stop
U0ACR start
16 cycles
16xbaud_rate