Slow
3x
Fast
Display input buffers
TDM Multiplexing Process - Real-time Data Flow
TS0: Sync
TS16: Signaling
Data Channels
Current Timeslot: TS0
Frame: 0
Channel: -
Data Value: 0x00
Input Buffer Status
Frame Timeline (125 µs)
0 µs
62.5 µs
125 µs
Input Streams
Multiplexer State
Rotation Counter
0
Selected Input
-
Output Register
00000000
E1 Output Stream
Recent Bytes
2.048 Mbps
Complete Frame Structure (256 bits)
Frame Alignment (TS0)
Signaling (TS16)
Voice/Data (TS1-15,17-31)
TDM Theory & Data Flow
Time Division Multiplexing Process
TDM divides the transmission time into fixed-length frames, each further divided into timeslots. In E1 systems:
- Each input channel is sampled at 8 kHz (every 125 µs)
- Samples are stored in input buffers awaiting their assigned timeslot
- The multiplexer rotates through channels at 8 kHz × 32 = 256 kHz
- Each channel gets 8 bits × 125 µs = 3.9 µs transmission time per frame
Input Buffering
Each channel has an 8-bit buffer that holds the PCM-encoded sample until its assigned timeslot arrives. Buffers prevent data loss during the waiting period.
Buffer State: [EMPTY] → [FILLING] → [FULL] → [TRANSMITTING] → [EMPTY]
Multiplexer Operation
The multiplexer acts as a high-speed rotary switch, connecting each input buffer to the output line for exactly 3.9 microseconds.
Switching Rate: 256,000 times/second
Contact Time: 3.90625 µs per channel
Contact Time: 3.90625 µs per channel
Laboratory Procedure
1
Observe Input Streams
Watch the analog waveforms on the left. Each color represents a different input channel.
2
Track Data Packets
Follow the colored packets as they move from input buffers through the multiplexer to the output stream.
3
Analyze Frame Assembly
Watch how the 32 timeslots are assembled. Note TS0 (red) and TS16 (yellow) special functions.