Q. I have tried to get “Modem One” to ‘talk’ to “Modem Two” but have been unsuccessful. How can I make the two on-board modem chips communicate?
A. The EV6240 was not designed to allow normal communications between its two on-board modem chips. The BERT test routine will allow both modems to communicate together, but this is only a test routine and not a normal operating mode.
Q. I have a EV6240 connected through a line simulator to my PC. I can't find any modem signals on the board. What could be wrong?
A. The problem could be a “ground loop”. Since we introduced the EV6240 we have found that users sometimes inadvertently and unknowingly create ground loops when they electrically attach non-isolated external equipment to the EV6240. Ground loops in any electrical circuit are notorious for causing strange operating problems.
To minimize the possibility of ground loops, CML recommends the following steps be performed:
a. Ensure that the EV6240 power supply is not referenced to earth
ground, either through its own power supply or by any piece of connected test
equipment. (Note: If any AC powered external equipment uses an AC plug without the third ground lead, it
can still introduce ground loops.
This is because the neutral lead is usually connected to ground in the
AC power source wiring. Truly isolated equipment will be electrically isolated from its ground, neutral, and
hot AC power leads and so will not create any ground loops.)
b. Remove jumpers JP9, JP10, JP11, and JP12. These jumpers allow for line voltage monitoring, but they also allow a ground loop to be formed.
c. The signals on the RS-232 serial cable from the PC are
referenced to whatever "ground" is used by the PC.
If the PC is being operated from a battery, no earth ground connection will come into play.
However, if the PC is AC powered, a ground loop can be formed. For this reason a separate +5V
power supply (again isolated from earth ground) should be connected to J8, and the switch
(SW2) should be placed in ISOLATE. Detailed instructions for this procedure are contained
elsewhere in the user manual.
Q. The EV6240 is connected through a line simulator to a PC. When I send an AT command to take the EV6240 off-hook, the line is taken off-hook but the board isn't connecting with an external modem. What could be the problem?
A. The problem may be that the EV6240 is not presenting enough DC loading to the telephone line simulator, and as a result, the line simulator doesn't know that the EV6240 is off-hook.
The DC off-hook resistance provided by R20 (Modem 1) and R48 (Modem 2) may be too large
to allow sufficient current flow to indicate an off-hook condition (for telephone line
simulators).
While the exact value of acceptable DC off-hook resistance is line simulator dependent,
resistances between 600 - 1000 W will typically yield satisfactory results. R20 and R48 are
socketed to allow for easy replacement.
Q. I am having trouble getting my EV6240 to operate correctly. Can you give me some tips?
A. While all of the necessary operating information is contained within the EV6240 user manual, the following is a “cookbook” procedure that can be used to get up and running on the EV6240 in a very short time:
b. Place EV6240 switch SW2 in “ISOLATE” position
c. NOTE: The EV6240 is pre-configured from the factory for 5.0V operation. For operation at different voltages, please refer to the EV6240 manual for the correct jumper manipulation.
a. This value depends on the telephone line simulator being used.
b. EV6240 is shipped with 2.2kohm DC off-hook load resistors, but this resistance has proved to be an inadequate load for some telephone line simulators.
b. CML bench testing indicates load resistor values of 600 to 800 ohms provide proper operation.
a. PROPERTIES
1. Under “Connect To” tab:
Under “Connect Using” pull down box, click ““Direct to COM1” or other as appropriate.
Click “Configure”, then select bps, data bits, etc, as appropriate.
Under “Settings” tab:
Select “VT100” for emulation mode
Select “ASCII Setup…”, select “Wrap lines that exceed terminal width”.
Select FILE > PROPERTIES
Under “Connect To” tab:
Under “Connect Using” pull down box, click “Lucent Win Modem” or other as appropriate
Click “Configure”, then…
Select bps, data bits, etc, as appropriate
b. Settings for flow control are contained in the “Advanced” menu under the
“Connections” tab
Under “Settings” tab:
a - Select “VT100” for emulation mode
Select “ASCII Setup…”, select “Wrap lines that exceed terminal width”
...sets control to Modem One (default)
...resets the modem IC
selects ITU standard mode
ATF0 - selects V.23 modulation
ATX0 - blind dialling” for the EV6240
AT& - configures modem to use the 2 wire line interface (default)
AT@B1 - enables Bell ringing signal detection
AT@E0 - sets “Modem Mode” (default)
ATB0 - configures modem for V.xx standards
ATM1 - PC speaker on until carrier present
ATN0 - forces connection at data rate specified in S Register (and at standard specified in ATBx command)
ATS37 - forces 1200bps connection
ATX0 - enables “blind dialling” on the part of the PC modem
ATS0=1 - enables auto answering after the first ring
Q. With respect to the EV8500, how do the FAT STUB and THIN STUB Interact?
Q. I have heard of the terms Thin Stub and Fat Stub, but I am not sure what their function is. Can you explain?
Q. How do the FAT STUB and THIN STUB relate to the onboard FLASH on the EV8500?
A. There are two ways of powering up the EV8500:
1. In a normal mode - When powered up in this mode the EV8500 will operate in a normal fashion as specified in the data sheet.
2. In Flash update mode - (Ref. section 6.6 of the EV8500 Manual = "To enter into FLASH programming mode remove the power from the EV8500 board and move the jumper link (JP10) from pins 2-3 (Normal Operation) to pins 1-2 (FLASH Programming). Connect the serial interface (J5) to a PC running the EV8500 FLASH programming application (EV8500_FLASH.EXE) and reconnect the power to the EV8500 board.").
When powered up in Flash update mode the EV8500 will operate in a Flash Upgrade or Upload Fashion. The jumper (JP10) pulls the Vbias line high thus enabling the Flash update mode.
Jumper (JP10) forces A16 high to run the thin stub already loaded into the FLASH memory.
In this mode the EV8500 execute the BOOT ROM (thin stub). The thin stub will load the FAT STUB, which facilitates FLASH programming.
The fat stub is loaded via the serial line and is never stored in the FLASH memory.
The current FAT STUB provided with the EV8500 is for the FLASH device fitted to the EV8500. If the designer wants to use a different FLASH device, then they must source or develop their own FAT STUB, which is suitable for programming the FLASH device they have chosen.
Q. I have just compiled my first piece of software for the EV8500 and the
Evaluation board is refusing to accept the new code?
The board is powered up and I am using the software application supplied with the EV8500
kit, what's wrong?
A. The EV8500 is often used as a starting point in the development of software, this process is made simpler as it is possible to download compiled software to the 512Kon-board external program FLASH via the EV8500 serial port from a PC without having to remove it and use an external ROM Programmer.
To make this process possible two software blocks called a “Thin Stub” and a “Fat stub” must be used, as they each have a very specific function to perform.
When the EV8500 is first powered up with on-board FLASH programming enabled (See EV8500 manual) the CMX850 program counter initially jumps to the location of the thin stub (10000h) already held in FLASH. The thin stubs sole task is to enable the CMX850 serial port and prepare the CMX850 to accept the Fat Stub.
When the PC is notified that the serial link between the EV8500 and itself is established it
immediately loads the Fat Stub into the CMX850 XRAM. Running from XRAM the Fat Stub
erases the external FLASH and waits for the next download.
The next download is the new compiled code.
To make all this possible the Thin Stub must always be resident in any compiled program resident in external FLASH. If it is not included, an initial serial link cannot be established and the Fat Stub cannot be installed in XRAM.
If this is the case the only realistic option is to program the FLASH memory externally with a suitable PROM Programmer, in this way the Thin Stub can be reintroduced to the FLASH at the correct location. If however you are unsure of how best to do this, the following hyperlink will allow you do download the original hex data (supplied by CML) stored in the Flash device: Intel Hex format right click to download. By programming the FLASH with an external PROM programmer the EV8500 Flash device will be restored to its original board settings.
Q. I have been trying to write my own code to the EV8500 Flash memory but keeping
getting the message: "Unable to reset FLASH memory for programming".
I have done everything the EV8500 manual tells me to do, such as
ensuring the thin stub is included in the new software but it still does not
work?
A. The likely scenario for this is that you are using the wrong type of FLASH
memory for the EV8500 board.
After changing the appropriate jumper settings and resetting the board, the thin stub
is next used to set-up the serial link to the local PC ready for the thick stub
to be downloaded.
Once the thick stub has been installed into XRAM, one of its first tasks is to validate
the FLASH memory.
This is performed by reading the unique identification number that is built into the FLASH,
if it does not read the code 29LV040 it will then flag an error.
Q. What component modification do I have to make to my DE8661 Board to make it CTR21 compliant?
Q. I want to improve/increase the return loss of my DE8661 board, How should I do this?
A. The DE8661 uses the same line interface as the DE8681 and is described in the same Application Note. To make this board CTR21 compliant and to reduce the return loss, please refer to the application note: CMX867 and CMX868 V.22bis and V.22 modem design guide (DAA reference design).
Q. What component modification do I have to make to my DE8681 Board to make it CTR21 compliant?
Q. I want to improve/increase the return loss of my DE8681 board, How should I do this?
A. To make this board CTR21 compliant and to reduce the return loses, please refer to the application note CMX867 and CMX868 V.22bis and V.22 modem design guide (DAA reference design)
Q. I seem to be having problems using my EV8810 kit with my P133 computer even though I am using Windows 98.
A. The EV8810 is controlled via the parallel port and requires that the data
transfer be very quick to fully service the onboard PIC Microcontroller.
The software supplied with the EV8810 achieves this rapid response by bypassing many
Windows conventions and disabling multi-tasking.
While this method is satisfactory with many of the latest PCs it is still not
sufficiently quick when using an older machine, the result is often corrupt and
incorrect responses or even the inability to connect to the EV8810 upon start-up.
Q.Will the EV9000 work correctly under Windows 95 and Windows 98 or
is it necessary to use Windows 3.1?
Does the age of he PC or its performance have an effect on compatibility?
A. The PC communicates directly with the FX9n9 device via minimal interface circuitry. There is no buffering micro-controller like those found in the other Evaluation Kits. All communication is via the PC parallel port and this must be accessed with a low latency to meet the timing requirements on the FX9n9. To ensure this, the Windows Scheduler is disabled in software giving processor time solely to the EV9000 application. This is okay in Windows 3.1 and can run in Windows 95 and 98 (remember however that Windows 3.1 sits on top of DOS which is not a multitasking OS unlike Windows 95 or Windows 98).
The type and age of PC’s can also cause problems with data
integrity when using them with the EV9000. Older machines can actually work better than
newer ones due to timing instabilities and I/O chipset implementations.
We have demonstrated operation on PCs running Windows 95 on P120 machines and are
aware of other customers using the EV9000 with Windows 98 on Pentium based, or similar,
machines.
Please note the CML disclaimer notice for applications and FAQ information.