User's Manual l TQMx50UC UM 0101 l © 2018 TQ-Group
Page 13
3.5.15
Serial Ports
The TQMx50UC offers a dual Universal Asynchronous Receiver and Transmitter (UART) controller. The register set is based on the
industry standard 16550 UART. The UART operates with standard serial port drivers without requiring a custom driver to be
installed. The 16 byte transmit and receive FIFOs reduce CPU overhead and minimize the risk of buffer overflow and data loss.
With the TQ-flexiCFG feature the serial ports can be configured to route the handshake signals to free pins at the COM Express™
connector.
Table 7:
Serial Port COM Express™ Port Mapping
COM Express™ Signal
COM Express™ Pin
TQMx50UC
Remark
SER0_TX
A98
SER0_TX
3.3 V output (without protection)
SER0_RX
A99
SER0_RX
3.3 V input (without protection)
SER1_TX
A101
SER1_TX
3.3 V output (without protection)
SER1_RX
A102
SER1_RX
3.3 V input (without protection)
SER0_RTS#
B98
SER0_RTS#
3.3 V output
SER0_CTS#
B99
SER0_CTS#
3.3 V input
SER1_RTS#
D24
SER1_RTS#
3.3 V output
SER1_CTS#
D25
SER1_CTS#
3.3 V input
Note: Protection circuits
In Revision 2.0 of the COM Express™ specification the signals A98, A99, A101 and A102 have been
reclaimed from the VCC_12V pool. Therefore protection on the TQMx50UC and on the carrier board is
necessary to avoid damage to those when accidentally exposed to 12 V. The implementation of this
circuitry causes lower transfer rates on the two serial ports.
On the TQMx50UC the protection circuit is removed by default and the serial ports provide transfer
rates of up to 115 kbaud. Therefore the TQMx50UC can only be used in a COM.0 Revision 2.0 Type 6
pinout carrier board.
3.5.16
Watchdog Timer
The TQMx50UC supports an independently programmable two stage Watchdog timer integrated in the TQ-flexiCFG block.
There are four operation modes available for the Watchdog timer:
•
Dual-stage mode
•
Interrupt mode
•
Reset mode
•
Timer mode
The Watchdog timer timeout ranges from 125 ms to 1 h.
The COM Express™ Specification does not support external hardware triggering of the Watchdog. An external Watchdog Trigger
can be configured to GPIO pins at the COM Express™ connector with the TQ-flexiCFG feature.
