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3.4
UART/RS-232 Connectors
This section describes the DB9 RS-232 serial interface connectors on the ADS. Each serial interface is
controlled by a UART that is either inside the i.MX21 processor or part of an external device.
3.4.1
UART1 Connector
Connector P1 connects to the UART1 pins of the i.MX21 MCU. UART1 is the primary functionality of
the pins. This female DB9 connector is configured for RS-232 DCE operation. Figure 3-5 shows pin
assignments and Table 3-5 provides signal descriptions for the connector.
Pin(s) Signal
1
CD
2
TXD
3
RXD
4
DTR
5
GND
6
DSR
7
RTS
8
CTS
9
RI
3-18
5
Figure 3-5. Connector P1 (UART1) DCE Pin Assignments
Table 3-5. Connector P1 (UART1) DCE Signal Descriptions
CARRIER DETECT — RS-232 output signal, pulled active positive
TRANSMITTED DATA — RS-232 serial data output signal
RECEIVED DATA — RS-232 serial data input signal
DATA TERMINAL READY — RS-232 input signal, the logic level signal is available at TP8
GROUND
DATA SET READY — RS-232 output signal, pulled active positive
READY TO SEND — RS-232 input signal, active positive
CLEAR TO SEND — RS-232 output signal, active positive
RING INDICATOR — RS-232 output signal, forced inactive negative
M9328MX21ADSE User's Manual, Rev. A
4
3
2
1
P1
9
8
7
6
Description
Freescale Semiconductor
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