A 'UL CLASS II' supply which complies with federal regulations for flammability and other types of failure is highly recommended! Ratings should be 7.5-12 VDC or 6-9 VAC with 400-1500 mA output.
The C31 DSK interface is designed to operate from either standard or bi-directional printer ports.
To communicate the DSK must have a valid communications kernel loaded and executing in its internal memory. The file that contains this kernel is C3X.ASM and the DSK3A output file C3X.DSK
If no port address is specified LPT1 is used. A scan of LPT1-LPT3 can also be specified (TEST option) but may take a few seconds while the scanning process attempts to establish a communications link. Since the scanning process sends data to each printer port, you may want to turn off all other printer port devices the first time you use this mode of the DSK. After the debugger starts you can find the LPT address by using the sF2 (shift and F2) keys to display the DSK's configuration information.
On startup, DSK applications software will typicaly check to see if the DSK will respond to kernel commands. If a link cannot be verified the initialization routine bootloads the file C3X.DSK into the DSK's internal memory.
If the application needs to load another file, that file must also be located within the current directory.
DSK files are created by the DSK3A assembler
The C31 DSK is designed to use either AC or DC wall mount supplies
'UL CLASS II' SUPPLIES WHICH COMPLY WITH FEDERAL REGULATIONS FOR FLAMMABILITY AND OTHER TYPES OF FAILURE ARE HIGHLY RECOMMENDED!
Voltage ratings should be 7.5-12VDC, or 6-9VAC, with current ratings between 400mA-1.5A. The power jack uses a 2.1mm coaxial jack which is common on many supplies. Note: A 2.5mm jack will fit but may be intermittent as the internal connector size's do not match.
LABORATORY TYPE SUPPLIES SHOULD BE USED WITH EXTREME CAUTION! THE 'OSHA' COMMON GROUND BETWEEN THE LAB SUPPLY, PC AND DSK CAN CREATE A GROUND LOOP OR SHORT IF NOT PROPERLY USED. THESE TYPES OF SUPPLIES ARE NOT RECOMMENDED FOR USE WITH THE DSK!
Laboratory supplies are typicaly grounded through the wall socket and or other safety grounds to prevent electrocution. However these grounds can also create ground loops with other equipment which can potentially create short circuits. In these cases the supply is typicaly shorted if a +V reference is used for ground essentially creating a short through the DSK's full wave rectifier.
The C31 DSK power supply uses a full wave rectifier to generate the +V supply from either AC or DC sources. A capacitive switching supply circuit (an LT1054) is then used to create the -V supply. The +/-V supplies are then regulated to +/-5V using LM7805 and LM7905 regulators.
The safe upper limit for +V, which is +15V, is determined by the voltage ratings of the +V bypass capacitors, the LT1054 and the thermal dissapation of the regulators.
The practical thermal power dissipation limit of the LM7805/LM7905 regulators which is ~3W if no heat sink is used. The printed wiring board (PWB) is designed to provide some heat sinking if the LM7805 is snugly bolted down to the board.
With no additional current loading from add on cards, the DSK consumes approximately 350mA from the +V supply. Therefor at 15V the LM7805 would need to dissipate (15V-5V)*350mA=3.5W which is too hot. With the recommended maximum 12V supply the dissipation drops to (12V-5V)*350mA = 2.45W which is hot but within limits.
External heat sinks can also be added as long as they do not electrically connect to other components. The pad under the LM7805 is connected to the internal ground plane and the LM7905 pad is floating. The TO-220 heat tab of the LM7805 is electrically grounded and the LM7905 connected to -V. A simple heat sink can be made from a piece of sheet metal (aluminum or copper) which is placed under the regulator and bent up along the regulators edge.
Two resetable fuses are also included to help safeguard against catastrophic failures. However these fuses are not designed to prevent all types of damage to the DSP and other components. Good design practices should always be used to make sure that the DSK components are not over stressed. The fuses are reset by disconnecting power and allowing them to cool.
Even if you know you have a bi-directional port, these ports are usually pre-configured as standard printer ports until they are enabled either by jumpers or by software setup (BIOS)
Knowing the correct port address is important since auto testing for the DSK can take a long time.
Printer ports that use weak pullups on the data lines can cause noise susceptibility in long cables. In these cases the DSK software drivers can be specified to have a longer timeout value using the T=xxx command line option.
Printer ports that use relatively strong pullups in the status return lines (used for host port acknowledge and nibble data return) can cause a slight voltage drops in the 100 ohm EMI filter resistors. At this time no incompatibilities are known, but if this is a problem try changing the EMI resistors to 50-75 ohms.
A small number of very early printer ports (8086 days!) are known to have open collector data pin drivers. In this case the printer port can replaced or pullups added to the data lines. Values are typicaly 330-1K ohms to Vcc.
Some security devices will allow the DSK to be used in a series pass through mode. You will need to test for reliability.
The correct cable to use is a straight through DB25 to DB25 cable. This cable will be MALE at one end and female at the other and should have ALL 25 pins connected. Be careful that you do not use a cable which is intended for RS232. RS232 cables are usualy easy to identify since some of the pins and receptacles are missing
DB25-DB25 Ribbon cables work nicely since they are easily identified as having all pins connected and have the good signal quality
The preferred cable length is less than 2 Meters (6 feet), but longer cables usualy work. Twisted pair cables where the data and control lines are coupled tend to create glitches.
The standard convention is that at the PC's back panel DB25 printer ports are male and RS232 ports are female. To make identification easy, look for a port on the back of the PC that the DSK can be directly plugged into. Basically you should not be able to plug the DSK into a DB25 RS232 port.
If you have other devices installed which use DB25 connectors, such as an XDS510, be sure not to connect the DSK to that port.
An unpopulated header location is provided on the DSK (JP4) for an XDS510 emulator. However, please be aware that the emulator halts the target processor effectively killing any DSK applications that communicates with the DSK via the printer port
DSK3D will crash unless the XDS510 emulator is free running
Be sure not to plug the DSK printer port cable into the XDS510, which also uses a DB25 for its port.
The communications kernel supplied with the DSK is designed to both communicate with the DSK's host port interface and also to perform debug functions such as single step, run, halt, context save and restore.
IT IS IMPORTANT NOT TO OVERWRITE THE KERNEL WITH YOUR APPLICATIONS CODE OR DATA!
THE KERNEL OCCUPIES THE LAST 256 WORD OF ON CHIP RAM.
Modified by John Loomis from TMS320C3X DSP Starter kit Updated Jan 13, 1999.