EAU-321 Multi Protocol Serial Port Card

This design greatly simplifies the deployment and maintenance of distributed systems - there is no need to upload configurations panel by panel, and only one download is needed to complete the entire network update.

Definition of Electrical Connections and Terminals

EAU-321 provides signal connection through two 20 bit terminal blocks X1 and X2. Understanding the definition of terminals is the key to proper wiring.

X1 terminal block

X1 corresponds to the signals of ports 1 and 2. The specific definition varies depending on the selected protocol:

RS232 mode (port 1/2):

Pin 1/11: DCD (Data Carrier Detection)

Pin 2/12: DTR (Data Terminal Ready)

Pin 3/13: RXD (receive data)

Pin 4/14: RTS (request to send)

Pin 5/15: TXD (transmit data)

Pin 6/16: CTS (Clear Send)

Pin 7/17: DTR (repeated)

Pin 8/18: RI (Ringing Indicator)

Pin 9/19: GND (signal ground)

Pin 10/20: NC (not connected)

RS422 mode (port 1/2):

Pin 3/13: TxD+(transmit positive)

Pin 4/14: TxD - (transmit negative)

Pin 5/15: GND

Pin 6/16: RxD - (receive negative)

Pin 7/17: RxD+(receive positive)

Other pins NC or not used

RS485 mode (port 1/2):

Pin 3/13: TxD/RxD+(positive data, bidirectional)

Pin 4/14: TxD/RxD - (Data Negative, Bidirectional)

Pin 5/15: GND

Other pins NC

RS485 mode is half duplex, and can only send or receive at the same time. The driving circuit automatically controls direction switching without the need for external RTS control.

X2 terminal block

X2 corresponds to ports 3 and 4, fixed as RS232. The pin allocation is similar to the RS232 mode of X1 (using pins 1-10 for port 3 and pins 11-20 for port 4), including complete DCD, RXD, TXD, DTR, GND and other signals.

Cable recommendations

The PDF specifically states that CAT-5 communication cables can be used. For long-distance applications of RS422/RS485, it is recommended to use shielded twisted pair cables (such as Belden 9841) and ground the shielding layer at one end. For RS232, it is recommended to use multi-core cables with overall shielding, with a maximum length of no more than 15 meters.

Detailed explanation of jumper configuration

The flexibility of EAU-321 largely comes from its jumper configuration. Correctly setting jumper wires is a prerequisite for the normal operation of the module. All jumpers are located on the PC/104 board and should be set up before installation.

J5 and J6- Protocol Selection

J5 and J6 are two multi jumper groups that control the protocol types of port 1 and port 2, respectively. Each port corresponds to a set of jumpers (J5 corresponds to port 1, J6 corresponds to port 2), with multiple independent jumpers inside each set used to define the connection method for each signal.

According to the table provided in the PDF, the jumper modes for each protocol are as follows:

Signal RS232 RS422 RS485

TxOut Note 1 Note 1 Note 1

RxOut Note 1 Note 1 Note 1

CTS Out In In

DCD Out In In

DTR Out In In

R1 Out In In

1 Out In In

2 In Out Out

3 Out In Out

4 Out Out In

5 In Out Out

6 Out Out In

Note 1: The specific jumpers for TxOut and RxOut need to refer to the silk screen of the board or the accompanying quick guide. Usually RS232 uses independent TXD/RXD cables; RS422/485 uses differential pairs.

In practical operation, engineers should refer to the silk screen markings on the EAU-321 board or the jumper diagram in the user manual. The key principle is that RS232 mode requires the connection of single ended signals such as RXD/TXD/CTS/RTS; RS422 mode requires both sending and receiving to be configured as differential pairs; RS485 mode combines sending and receiving on the same pair of differential lines and enables internal direction control.

J8- Interrupt Setting

J8 is used to set the interrupt line. The PDF clearly states that J8 must be set to interrupt 7 and R. This means that EAU-321 will occupy IRQ7 resources. In PC/104 systems, IRQ7 can usually be used for expansion cards, but it is necessary to ensure that there are no conflicts with other devices. If there are multiple communication boards in the system, each board's J8 needs to be set to IRQ7, and different boards need to be distinguished through upper layer software.

J9, J10, J11- Port Interruption

These three jumper groups are used to configure interrupt allocation for each port. The PDF requires all ports to be set to interrupt 7. This means that when any port experiences data reception or a change in line status, the same IRQ7 interrupt will be triggered. The driver program identifies which port caused the interrupt by reading the interrupt status register on the board. This design simplifies interrupt management and is suitable for a polling/interrupt hybrid mode.

J7- Board Address

J7 is used to set the I/O base address of the PC/104 bus. The PDF clearly states that jumper positions A and B must be set to In. This setting applies to all communication boards and corresponds to a base address of 100h (hexadecimal). This means that EAU-321 occupies an I/O address range of around 100h-10Ph (specific mapping depends on internal registers). If multiple EAU-321 cards are installed in the system or have address conflicts with other PC/104 cards, it is necessary to avoid conflicts through other means such as software configuration or different types of cards. However, according to system limitations, each system unit can only support a maximum of one EAU-321, so address conflicts usually do not occur.