UM10346_1
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 01 — 2 November 2009
58 of 132
NXP Semiconductors
UM10346
LPC980/982 User manual
10.8 Framing error
A Framing error occurs when the stop bit is sensed as a logic 0. A Framing error is
reported in the status register (SSTAT). In addition, if SMOD0 (PCON.6) is 1, framing
errors can be made available in SCON.7. If SMOD0 is 0, SCON.7 is SM0. It is
recommended that SM0 and SM1 (SCON[7:6]) are programmed when SMOD0 is logic 0.
10.9 Break detect
A break detect is reported in the status register (SSTAT). A break is detected when any 11
consecutive bits are sensed low. Since a break condition also satisfies the requirements
for a framing error, a break condition will also result in reporting a framing error. Once a
break condition has been detected, the UART will go into an idle state and remain in this
idle state until a stop bit has been received. The break detect can be used to reset the
device and force the device into ISP mode by setting the EBRR bit (AUXR1.6)
Table 47.
Baud Rate Generator Control register (BRGCON - address BDh) bit description
Bit Symbol
Description
0
BRGEN
Baud Rate Generator Enable. Enables the baud rate generator. BRGR1 and
BRGR0 can only be written when BRGEN = 0.
1
SBRGS
Select Baud Rate Generator as the source for baud rates to UART in modes 1 and
3 (see
for details)
2:7 -
reserved
Fig 24. Baud rate generation for UART (Modes 1, 3)
baud rate modes 1 and 3
SBRGS = 1
SBRGS = 0
SMOD1 = 0
SMOD1 = 1
timer 1 overflow
(PCLK-based)
baud rate generator
(CCLK-based)
002aaa897
÷
2
Table 48.
Serial Port Control register (SCON - address 98h) bit allocation
Bit
7
6
5
4
3
2
1
0
Symbol
SM0/FE
SM1
SM2
REN
TB8
RB8
TI
RI
Reset
x
x
x
x
x
x
0
0
Table 49.
Serial Port Control register (SCON - address 98h) bit description
Bit Symbol
Description
0
RI
Receive interrupt flag. Set by hardware at the end of the 8th bit time in Mode 0, or
approximately halfway through the stop bit time in Mode 1. For Mode 2 or Mode 3,
if SMOD0, it is set near the middle of the 9th data bit (bit 8). If SMOD0 = 1, it is set
near the middle of the stop bit (see SM2 - SCON.5 - for exceptions). Must be
cleared by software.
1
TI
Transmit interrupt flag. Set by hardware at the end of the 8th bit time in Mode 0, or
at the stop bit (see description of INTLO bit in SSTAT register) in the other modes.
Must be cleared by software.
2
RB8
The 9th data bit that was received in Modes 2 and 3. In Mode 1 (SM2 must be 0),
RB8 is the stop bit that was received. In Mode 0, RB8 is undefined.