Serial Port Complete - Latest Microcontroller projects

Inside RS-232

Table 4-4: In addition to RS-232, there are several other EIA/TIA interfaces for
unbalanced lines.

   +"')/)'1 +"2"'-)/' +"'*3) +"'*/4'

Cable length, max

(ft), unshielded

cable, 20pF/ft,

100kbps

50 50 15 ft @ 64kbps 4000

Data rate, max

(bps)

20k 100k 64k 2.1M

Driver output

(minimum, V)

± 5 ± 3.6 ±3.3 ± 3.3, ±2*

Driver output

(maximum, V)

± 15 ± 6 ±13.2 ±6, ±10*

Receiver

sensitivity (V)

± 3 ± 0.2 ± 3 ±0.2

Maximum

number of drivers

1111

Maximum

number receivers

110110

Receiver input

resistance (Ω)

3k-7k 450 (minimum) 3k-7k 450, 4k*

*Data and some control lines use a balanced interface. Other signals use an unbalanced interface.

Figure 4-6: An RS-423 interface can have just one transmitter but can have up to ten

receivers.