1. Chapter 6. Data Communications Interface
Asynchronous and Synchronous Transmission
Line Configurations
Interfacing

2. Asynchronous Transmission
E.g. NRZ-L signaling
Remain
idle or next
start bit
Idle state
of line
Start
bit
1~2 bit times
5 to 8 data bits P
bit
Stop
(a) Character format
Start
bit
Start
bit
Stop
bit 1 1 1 1 1 1 1
1 ...
(b) 8-bit asynchronous character stream

3. Synchronous Transmission
Separate clock line, or
Embed the clocking information in the data signal
E.g. Manchester or Differential Manchester encoding

4. Line Configurations Topology Full Duplex or Half Duplex Point-to-point
Multi-point
Full Duplex or Half Duplex

5. Interfacing DTE DCE data terminal equipment: terminals and computers
data circuit-terminating equipment: modem

6. Interfacing (cont)

7. Interfacing (cont) Four important characteristics E.g. V.24/EIA-232-E
Mechanical
Electrical
Functional
Procedural
E.g. V.24/EIA-232-E
RS232 in 1962  5th revision in 1991
Mechanical: ISO 2110
Electrical: V.28
Functional: V.24
Procedural: V.24

8. V.24/EIA-232-E

9. V.24/EIA-232-E Dial-up Operation

10. V.24/EIA-232-E Dial-up (cont)

11. V.24/EIA-232-E Dial-up (cont)