phyCORE-TC1796
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©
PHYTEC Meßtechnik GmbH 2009 L-719e_2
7
Serial Interfaces
7.1
RS-232 Interface (U5)
One dual-channel RS-232 transceiver is located on the phyCORE-
TC1796 at U5. This device converts the signal levels for the
RXD0_TTL and TXD0_TTL lines, as well as those of the second
serial interface, RXD1_TTL and TXD1_TTL from TTL level to
RS-232 level. The RS-232 interface enables connection of the
module to a COM port on a host-PC. In this instance the RxD0 line
of the transceiver is connected to the TxD line of the COM port;
while the TxD0 line is connected to the RxD line of the COM port.
The Ground potential of the phyCORE-TC1796 circuitry needs to be
connected to the applicable Ground pin on the COM port as well.
The microcontroller’s on-chip UART does not support handshake
signal communication. However, depending on user needs, hand-
shake communication can be software emulated 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.
Furthermore there is the possibility of using the TTL signals of the
two UART channels externally. These are available on the
phyCORE-connector at X3C19, X3C20 (RXD1_TTL, TXD1_TTL)
and X3D16, X3D17 (RXD0_TTL, TXD0_TTL). This becomes
necessary if galvanic isolation of the interface signals is required.
The TTL transceiver outputs of the on-board RS-232 device can be
decoupled from the receive signals RXD0_TTL and RXD1_TTL via
solder jumpers J31 and J33. This is necessary so that no external
transceivers drive signals against the on-board transceiver. The
transmit signals TXD0_TTL / TXD1_TTL, in contrast, can be
connected parallel to the transceiver inputs, without causing a
collision.
