UM10147_2
© NXP B.V. 2008. All rights reserved.
User manual
Rev. 02 — 28 April 2008
64 of 134
NXP Semiconductors
UM10147
P89LPC952/954 User manual
10.12 More about UART Modes 2 and 3
Reception is the same as in Mode 1.
The signal to load S0BUF and RB8_n, and to set RI_n, will be generated if, and only if, the
following conditions are met at the time the final shift pulse is generated. (a) RI_n = 0, and
(b) Either SM2_n = 0, or the received 9th data bit = 1. If either of these conditions is not
met, the received frame is lost, and RI_n is not set. If both conditions are met, the
received 9th data bit goes into RB_n, and the first 8 data bits go into SnBUF.
10.13 Framing error and RI_n in Modes 2 and 3 with SM2_n = 1
If SM2_n = 1 in modes 2 and 3, RI_n and FE_n behaves as in the following table.
Fig 23. Serial Port Mode 1 (only single transmit buffering case is shown).
transmit
start
bit
stop bit
INTLO = 0
TX clock
write to
SBUF
shift
TXD
TI
D0
D1
D5
D2
D6
D3
D4
D7
receive
RX
clock
shift
RI
start
bit
stop bit
RXD
D0
D1
D5
D2
D6
D3
D4
D7
002aaa926
÷
16 reset
INTLO = 1
Fig 24. Serial Port Mode 2 or 3 (only single transmit buffering case is shown).
transmit
start
bit
stop bit
stop bit
TX clock
write to
SBUF
shift
TXD
TI
D0
D1
D5
D2
D6
D3
D4
D7
receive
RX
clock
shift
RI
start
bit
RXD
D0
D1
D5
D2
D6
D3
D4
D7
002aaa927
TB8
RB8
÷
16 reset
INTLO = 0
INTLO = 1
SMOD0 = 0
SMOD0 = 1