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© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
User manual Rev. 02 — 23 May 2005 61 of 133
Philips Semiconductors
UM10109
P89LPC932A1 User manual
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 50: 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
Resetxxxxxx00
Table 51: 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.
3 TB8 The 9th data bit that will be transmitted in Modes 2 and 3. Set or clear by software
as desired.
4 REN Enables serial reception. Set by software to enable reception. Clear by software to
disable reception.
5 SM2 Enables the multiprocessor communication feature in Modes 2 and 3. In Mode 2 or
3, if SM2 is set to 1, then Rl will not be activated if the received 9th data bit (RB8)
is 0. In Mode 0, SM2 should be 0. In Mode 1, SM2 must be 0.
6 SM1 With SM0 defines the serial port mode, see Tabl e 52
.
7 SM0/FE The use of this bit is determined by SMOD0 in the PCON register. If SMOD0 = 0,
this bit is read and written as SM0, which with SM1, defines the serial port mode. If
SMOD0 = 1, this bit is read and written as FE (Framing Error). FE is set by the
receiver when an invalid stop bit is detected. Once set, this bit cannot be cleared
by valid frames but is cleared by software. (Note: UART mode bits SM0 and SM1
should be programmed when SMOD0 is logic 0 - default mode on any reset.)
Table 52: Serial Port modes
SM0, SM1 UART mode UART baud rate
00 Mode 0: shift register
CCLK
⁄
16
(default mode on any reset)
01 Mode 1: 8-bit UART Variable (see Tabl e 47
)
10 Mode 2: 9-bit UART
CCLK
⁄
32
or
CCLK
⁄
16
11 Mode 3: 9-bit UART Variable (see Tabl e 47)