PEP CP351, Manual

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CP351 Introduction
ID 18983, Rev. 0101 Page 1 - 9 ® PEP Modular Computers GmbH
For the realization of plug & play compatibility it is possible to programm certain QSPAN
registers from a serial EEPROM at system reset or power up.
1.6 Fieldbus Interface
The fieldbus interface is an opto-isolated RS485 interface providing RxD and TxD lines.
The RTS signal is used to enable the transmitter and the serial interface is opto-isolated
between the ASPC2 and the transceiver.
The RS485 interfaces are routed to a 9-pin D-Sub connector. This interface is used in
conjunction with external connectors providing integrated termination, as the PROFI-
BUS interface itself is not provided with termination resistors. A list of recommended
external connectors is given in chapter 3 of this manual.
A zero ohm resistor is also present on the board to disconnect the local supply from the
fieldbus. This is used for those applications that may require an external supply. The
standard installation is with isolated 5V termination power.
1.6.1 On-Board Bus Error Timer
The CP 351 provides an on-board bus error timer monitoring the cycle lengths of data
transfers to and from locations beyond the CPU data bus buffer.
1.6.2 Watchdog Timer
The on-board system reset generator is triggered at timeout by a watchdog timer.