Following is my test procedure for 841M.EXE under VC Example directory.

System configuration :

WINNT 4.0 Workstation+SP4
PCL-841 Port1 DA00, IRQ7
                  Port2 DA20, IRQ9
9-pin PIN TO PIN Cable for the connection of PORT1 and PORT2
Terminate Resistors are installed.


Test Procedures.

1. Device Installation
     Add CAN1 I/O=DA00 Interrupt=7 :
     PORT=1,  Interrupt=7, HOST ID=63, Memory Address=DA00, Baud Rate 500Kbps, DeviceNet
     Add CAN2 I/O=DA20 Interrupt=9 :
     PORT=2,  Interrupt=9, HOST ID=64, Memory Address=DA20, Baud Rate 500Kbps, DeviceNet

2. Run 841M.EXE
   (1) Run 1st 841M.EXE
         Interrupt Mask=3(transmit and receive interrupts are enabled) => Click CANPortOpen => 
         CANHwReset  => CANReset => CANSetBaud => CANSetAcp => CANSetOutCtr => CANInit
         => Handling Event => CANEnabledMessaging => CANSetNormal
       ( It is not necessary to click the checkbox of Enable Receive Interrupt, Enable Transmit 
          Interrupt, Enable Error Interrupt, Enable Overrun Interrupt if we don't want to receive 
          messaging Function in our test program. )
    (2) Run 2nd 841M.EXE
         Interrupt Mask=3(transmit and receive interrupts are enabled) => Click CANPortOpen => 
         CANHwReset  => CANReset => CANSetBaud => CANSetAcp => CANSetOutCtr => CANInit
         => Handling Event => CANEnabledMessaging => CANSetNormal
        ( It is not necessary to click the checkbox of Enable Receive Interrupt, Enable Transmit 
          Interrupt, Enable Error Interrupt, Enable Overrun Interrupt if we don't want to receive 
          messaging Function in our test program. )
     (3) Connect PORT1 and PORT2
**  (4) Click Register => Refresh => Close in both 1st and 2nd 841M.EXE
     (5) In Transmit Message ID and Message fields of 2nd 841M.EXE, enter ID=1234, 
           Message=aaaaaaaa => Click CANSendMsg
      (6) You can find 2 popup message box indicating PORT1 Event ! and PORT2 Event !
      (7) Click CANQueryMsg buttom of 1st 841M.EXE and you will find the message aaaaaaaa.
  ** (8) Click Register => Refresh => Close in both 1st and 2nd 841M.EXE
      (9) In Transmit Message ID and Message fields of 1st 841M.EXE, enter ID=2222, 
           Message=dddddddd => Click CANSendMsg
      (10) You can find 2 popup message box indicating PORT1 Event ! and PORT2 Event !
      (11) Click CANQueryMsg buttom of 2nd 841M.EXE and you will find the message dddddddd. 
      (12) Repeat (4) to (11)...

** The Event message box will not popup if you don't refresh the register. It is very important!!

Please also refer to PCL-841 User's Manual Page 33 Register Address Map Interrupt Register.
The value for this register is equal to the value of Interrupt Mask in 841M.EXE.
For example, if Interrupt Mask=3, the transmit and receive interrupts are enabled. It means you will get Event Message Boxes while both tranmitting and receiving messages.