Singular matrix error in 60 second timer

[crazybmanp]

i am getting the following error report in my circuit, the problem is, from what i can tell the error is in a perfectly hooked up seven segment display.

this circuit is for my DE class so i have used only 74LS chips i wanted to show my teacher how to use Hierarchical blocks, to make cleaner looking files for a side project where we use alot of different gates and we want to keep it organized.

the problem is, after i made the block "2nd" which is a simple 3 bit asynchronous counter, i am getting this error:

| Output from instrument analysis
| | vv1: no DC value, transient time 0 value used
| | singular matrix: check nodes adac1in:xu9.qc#branch_1_0 and adac1in:xu9.qc#branch_1_0
| | singular matrix: check nodes adac1in:xu9.qc#branch_1_0 and adac1in:xu9.qc#branch_1_0
| | singular matrix: check nodes adac1in:xu9.qc#branch_1_0 and adac1in:xu9.qc#branch_1_0
| | singular matrix: check nodes adac1in:xu9.qc#branch_1_0 and adac1in:xu9.qc#branch_1_0
| | singular matrix: check nodes adac1in:xu9.qc#branch_1_0 and adac1in:xu9.qc#branch_1_0
| | TRAN: Timestep too small; initial timepoint:trouble with (dledseg:xu2) d1:xu2
| | Error: doAnalyses: Timestep too small
| |
| |
| | tran simulation(s) aborted

attached is the circuit files (set up to read all of the sub-circuits from National Instruments/Circuit Design Suite 10.1 in your documents folder) circuit is the file you should open

[Tien_P]

Hi,

Digital models in Multisim are behavioral model, what that means is the inputs/output pins are either high/low state. There are pin drivers running in the background that convert input/output pins to a voltage such as 5V or 0V so that digital components can work with  analog components.  Your circuit problems appears to be a pin driver issue and and it's failing to do mix-mode simulation. I was able to fix the circuit by connecting 1ohm resistors to U9 and the subcircuit "2trigger".  

Attached is a modified file that is simulating. 

Best regards,

Tien Pham