Serial mode definition – Maxim Integrated MAXQ7666 User Manual
Page 224
MAXQ7665/MAXQ7666 User’s Guide
6-6
Serial Mode Definition
Bit 6: Serial Port Mode Bit 1 (SM1). See the
Serial Mode Definition table.
Bit 5: Serial Port Mode Bit 2 (SM2). Setting this bit in mode 1 ignores received data if an invalid stop bit is detected. Setting this bit
in mode 2 or 3 enables multiprocessor communications, and prevents the RI bit from being set and the interrupt from being asserted
if the 9th bit received is 0. See the
Serial Mode Definition table. This bit also used to support mode 0 for clock selection.
SM2 = 0: System clock is divided by 12.
SM2 = 1: System clock is divided by 4.
Bit 4: Receive Enable (REN)
REN = 0: Serial port 0 receiver disabled.
REN = 1: Serial port 0 receiver enabled for modes 1, 2 and 3. Initiate synchronous reception for mode 0.
Bit 3: 9th Transmission Bit State (TB8). This bit identifies the state of the 9th transmission bit in serial port modes 2 and 3.
Bit 2: 9th Received Bit State (RB8). This bit identifies the state of the 9th bit of received data in serial port modes 2 and 3. When SM2
is 0, it is the state of the stop bit in mode 1. This bit has no meaning in mode 0.
Bit 1: Transmit Interrupt Flag (TI). This bit indicates that the data in the serial port data buffer has been completely shifted out. It is
set at the end of the last data bit for all modes of operation and must be cleared by software once set.
Bit 0: Receive Interrupt Flag (RI). This bit indicates that a data byte has been received in the serial port buffer. The bit is set at the
end of the 8th bit for mode 0, after the last sample of the incoming stop bit for mode 1 subject to the value of the SM2 bit, or after the
last sample of RB8 for modes 2 and 3. This bit must be cleared by software once set.
UART MODE
SM2
SM1
SM0
FUNCTION
LENGTH (BITS)
PERIOD
0
0
0
0
Synchronous
8
12 System Clock
0
1
0
0
Synchronous
8
4 System Clock
1
X
1
0
Asynchronous
10
64/16 Baud Clock
(SMOD = 0/1)
2
0
0
1
Asynchronous
11
64/32 System Clock
(SMOD = 0/1)
2
1
0
1
Asynchronous (MP)
11
64/32 System Clock
(SMOD = 0/1)
3
0
1
1
Asynchronous
11
64/16 Baud Clock
(SMOD = 0/1)
3
1
1
1
Asynchronous (MP)
11
64/16 Baud Clock
(SMOD = 0/1)
Maxim Integrated