To get into TINA in more detail, open the second example, the file PIC flasher origin.TSC
project from TINA’s Examples/PCB folder. Press the 2D/3D View button in the toolbar
and look at the schematic of the flasher.
The schematic is PCB-ready–as you can verify by pressing the 2D/3D button, every part
has a surface mount device (SMD) physical representation. Now, before we start the PCB
wizard, click Tools/Footprint Name Editor… to check the footprints list.
Since all the components appear to have a valid footprint name, we can start using the
Tools/PCB Wizard. Set the “Start new project,” check “Autoplacement” and “Use
board template.” Browse for the template file “2layer_B_mm.tpt.”
Review actual physical parts, if possible. Be sure to allow for the area of all the
components, mounting holes, and keep-away zones and make your best estimate of the
values for Board width and Board height. Moreover, it is important to provide
enough space between the components to allow for the placement of vias and tracks
during routing. Enter 40mm length and 30mm width.
Press the OK button, ignore the Electric Rule Check warning, and save the board as PIC
The components are placed in the close proximity to minimize the connection lengths, in
a topology similar to that of the schematic, while still respecting the design rule settings.
However convenient the result may be for autorouting, the designer usually has to make
adjustments to the component layout to satisfy electrical, mechanical and other
characteristics. Some of the considerations are––
• the ohmic effect of a long and/or thin power tracethe length of a track from
the signal source to the load in high-speed digital systems introduces reflections
• in analog situations, poor placement can lead to increased noise coupling
• allowance for automated parts placement clearance
• future serviceability of the PCB
• aesthetic values
These considerations influence the components’ position and could be critical–not only in
complex designs–but even in the simplest ones. For these reasons, one must still adjust
parts placement manually.
Our circuit, although it is small and not very dense, has a few special requirements,
namely to put the crystal closer to the microcontroller, to position the power supply
connector, and to adjust the LEDs along the board.
If you want to change the board size, click the “Draw/modify shapes” button .
Let’s try making the board smaller. You can double click on the middle of the board and
enter the following values into the fields:
When you press OK, the board outline will shrink.
Now, before we begin routing, let’s set the position of the components; place the power
connector and the DIP switch on the left hand side and the LED bar on the right
hand side. Place the capacitors and resistor networks on the bottom side by double
clicking on the components and choosing Bottom Placement side on the dialog.
Compare your result to the file \Examples\PCB\PIC flasher placed.tpc.
In order to decrease route length, swap R1 pins connected to SW1. Pin swapping is
allowable if identically functioning pins are to be exchanged, such as pins of resistors,
capacitors, etc. Click on the Pinswap button on the toolbar to pick up the tool, click
on pad 1 of R1 (the upper right), and–finally–pad 4 of R1. The following window should
Press the Yes button, then do the same with R1 pad 2,3 and R2 pad 3,4.
Note that a pin swap changes the original connections, so we must update the original
schematic later to maintain the correspondence between the schematic and the board taking into
account the changes we made to the board while using PCB Designer. This process,
called backannotation, has to be completed whenever a pin/gate swap and/or component
renaming have been performed.
Signal planes (in our present example, the top and bottom layers) generally are given
preferred trace directions up and down in one layer and left and right in the other layer. To
set these trace directions, click on Options/Autorouter settings. The Autorouter
settings are set to our preferred direction by choosing an integer number from 1 to 9.
A value of 1 forces the router to heavily emphasize horizontal lines, while a value of 9
forces it to use vertical lines. 5 tells the router not to care about horizontal or vertical
preference. Choosing the extreme values (1 and 9 for a pair) is usually too strict, so we
choose to enter 3 for the top layer and 7 for the bottom.