IA186ES/IA188ES
Data Sheet
8-Bit/16-Bit Microcontrollers
November 15, 2011
Serial Port MODE Settings
Data Parity Stop
MODE
Description
Bits
Bits
Bits
a
Data Mode 0
7
–
2
0
1
2
3
4
Data Mode 1 7 or 8 1 or 0
Data Mode 2
Data Mode 3 8 or 9 1 or 0
Data Mode 4
Data Mode 5 7 or 8 1 or 0
Data Mode 6
Data Mode 7 8 or 9 1 or 0
1
1
1
1
9
–
7
–
a
2
5
a
9
0
2
6
a
2
7
a
These were originally reserved modes that have
been implemented to provide 2 stop bits.
– Mode 2 requires that the ninth data is set to a 1 state. Otherwise, the character will be
ignored by the receiver. The transmit section, however, operates as if it were in
Mode 3.
– This is designed to facilitate multidrop communication over a common serial data
link. For this purpose, the port in question is initially programmed to mode 2 and for
each data received with the ninth bit (Bit [8]) set as 1. It is compared by software
with a unique identifier for this port. If the identifier comparison does not find a
match, the port is left in mode 2. If the comparison finds an identifier match, the port
should be reprogrammed to mode 3 so that the ninth bit is allowed to be 0.
– Handshaking should only be employed in such a multidrop system by ports that are
exchanging data (mode 3) to prevent multiple ports from attempting to drive the
handshake signals. Mode 2 does not support handshaking for this reason and should
not be enabled. If it is possible that more than 2 ports be configured in mode 3 at the
same time, handshaking should not be implemented.
– Mode 3 allows for 8 data bits if parity is enabled or 9 data bits if parity is not enabled.
If parity is not used, the ninth data bit for the transmit section is set by writing a 1 to
the TB8 bit in the serial port control register. The ninth bit is read at the receive port
from the RB8 bit in the serial port status register.
– Mode 4 allows for a start bit, 7 data bits, and a stop bit without parity, which is not
available.
5.1.27 PDATA1 (07ah) and PDATA0 (074h)
PIO DATA Registers. When a PIO pin is configured as an output, the value in the
corresponding PIO data register bit is driven onto the pin. However, if the PIO pin is configured
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