SD188ES/SD188EM Demonstration Board User’s Manual
2-8
1.1
RS-232 Serial Ports
The ES version of the SD188ES/SD188EM demonstration board provides two on-
board RS-232 serial ports (P0, P1) that are directly driven by the Am188ES
microcontroller. The serial ports are equipped with DB-9 DCE connectors. The
pin assignment for the DB-9 connectors is shown in Figure 2-4 on page 2-9.
The EM version of the SD188ES/SD188EM demonstration board provides one
on-board RS-232 serial port that is directly driven by the Am188EM
microcontroller. The RS-232 serial port (P1) is equipped with a DB-9 DCE
connector. The pin assignment for the DB-9 connector is shown in Figure 2-4 on
page 2-9.
The Am188EM serial port does not provide RTS and CTS support in hardware.
The PSC3 and PSC2 pins are wired to the corresponding signals and can be
configured as PIO outputs for limited RTS and CTS support via software.
Traditionally, PCs have Data Terminal Equipment (DTE) ports which connect
directly to the Data Communication Equipment (DCE) port on the SD188ES/
SD188EM demonstration board. A null modem cable is not required to connect a
DTE port with a DCE port.
The RS-232 specification calls for signals that are driven at non-TTL levels. Single-
chip RS-232 driver/receiver devices (MAX232, U5 and U6) are used to convert to
and from the required voltages.
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