Electronics Tutorials - Dallas
DS80C320 Tutorial - Secondary Serial Port
A very useful feature provided by the
DS80C320 is the availability of a second serial port (UART). The
second serial port functions almost identically to the original
port with its own set of SFRs to control it. Both serial ports
may be used simultaneously and may operate at different baud
rates.
The original serial port is referred to as serial port 0
and the new secondary port is referred to as serial port 1.
All SFRs that are related to serial communications are appended
with a "0" in the case of serial port 0 and with a "1" in the
case of serial port1. Thus, the 8052s SBUF SFR is now
called SBUF0 and the DS80C320s new SFR to read and write
from its secondary port is called SBUF1. At the hardware
level, P1.2 (RXD1) is used for reception of data
on serial port 1 and P1.3 (TXD1) is used for the
transmission of data.
The control of the new serial port is identical to the
original 8052 serial port, but you must use the SFRs that
control the new port. They are:
Original Serial Port SFR
Secondary Serial Port SFR
Secondary Serial Port SFR Address
SCON
SCON1
C0h
SBUF
SBUF1
C1h
Note that while the 8052s standard serial port can use either
Timer 1 or Timer 2 to generate baud rates, the secondary serial
port on the DS80C320 may only use Timer 1. However, both serial
ports may use timer 1 simultaneously if so desired.