phyCORE-P8xC51Mx2
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PHYTEC MMesstechnikGmbH 2005 L-602e_3
5
Serial Interfaces
5.1
RS-232 Interface
An RS-232 transceiver is located on the phyCORE-P8xC51Mx2 at
U9. This device adjusts the signal levels of the P3.0/RxD0,
P3.1/TxD0, P4.0/RxD1 and P4.1/TxD1 lines. The RS-232 interface
enables connection of the module to a COM port on a host-PC. In this
instance, the RxD0 line (X1F15) of the transceiver is connected to the
TxD line of the COM port; while the TxD0 line (X1F14) is connected
to the RxD line of the COM port. The ground circuitry of the
phyCORE-P8xC51Mx2 is also connected to the applicable ground pin
on the COM port.
The microcontroller’s on-chip UART does not support handshake
signal communication. However, depending on user needs, handshake
communication can be replicated using port pins on the
microcontroller. Use of an RS-232 signal level in support of
handshake communication requires use of an external RS-232
transceiver not located on the module.
5.2
RS-485 Interface
As an alternative to the RS-232 interface, an RS-485 interface can be
configured on the phyCORE-P8xC51Mx2 using the lines P4.0/RxD1
and P4.1/TxD1. Jumpers J10 - J13 enable selection between RS-232
and RS-485 interfaces (see sections 3.7 and 3.8).
The RS-485 transceiver (U11) supports up to 32 nodes in one bus
system. Data transmission occurs via differential signal levels
according to RS-485 interface standards.
Note:
To utilize the RS-485 interface, Jumper J14 must be closed. This
enables control of the transmit function on the RS-485 transceiver IC
via port 1.5 (refer to section 3.9).
