UM10346_1
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 01 — 2 November 2009
59 of 132
NXP Semiconductors
UM10346
LPC980/982 User manual
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
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 50.
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
10
Mode 2: 9-bit UART
CCLK
⁄
32
or
CCLK
⁄
16
11
Mode 3: 9-bit UART
Variable (see
Table 51.
Serial Port Status register (SSTAT - address BAh) bit allocation
Bit
7
6
5
4
3
2
1
0
Symbol
DBMOD
INTLO
CIDIS
DBISEL
FE
BR
OE
STINT
Reset
x
x
x
x
x
x
0
0
Table 52.
Serial Port Status register (SSTAT - address BAh) bit description
Bit Symbol
Description
0
STINT
Status Interrupt Enable. When set = 1, FE, BR, or OE can cause an interrupt. The
interrupt used (vector address 0023h) is shared with RI (CIDIS = 1) or the
combined TI/RI (CIDIS = 0). When cleared = 0, FE, BR, OE cannot cause an
interrupt. (Note: FE, BR, or OE is often accompanied by a RI, which will generate
an interrupt regardless of the state of STINT). Note that BR can cause a break
detect reset if EBRR (AUXR1.6) is set to logic 1.
1
OE
Overrun Error flag is set if a new character is received in the receiver buffer while it
is still full (before the software has read the previous character from the buffer),
i.e., when bit 8 of a new byte is received while RI in SCON is still set. Cleared by
software.
2
BR
Break Detect flag. A break is detected when any 11 consecutive bits are sensed
low. Cleared by software.
3
FE
Framing error flag is set when the receiver fails to see a valid STOP bit at the end
of the frame. Cleared by software.
Table 49.
Serial Port Control register (SCON - address 98h) bit description
…continued
Bit Symbol
Description