Information Technology Reference
In-Depth Information
int get_character(void)
{
int status;
do
{
status = _inp(LSR) & 0x01;
} while (status!=0x01); /* Repeat until bit 1 in LSR is set */
return( (int)_inp(TXDATA));
}
13.6 Exercises
13.6.1
Which is the maximum cable length for a standard RS-232 connection:
(a)
2 m
(b)
2 0m
(c)
200 m
(d)
2 km
13.6.2
Which enhancement to RS-232 allows for 1Mbps bit rates and increased cable
lengths:
(a)
RS-232x
(b)
RS-422
(c) RS-444 (d) RS-233
13.6.3
Which of the following is not a standard RS-232 bit rate:
(a)
110 bps
(b)
4800 bps
(c)
9600 bps
(d)
12 200 bps
13.6.4
Which voltage range is used for a '0' bit value:
(a)
-3 V to -25 V
(b)
0 V to -3 V
(c)
+3 V to +25 V
(d)
0 V to +3 V
13.6.5
In RS-232, how is the inactive period identified:
(a)
A high voltage level
(b)
A low voltage level
(c)
Zero voltage level
(d)
Open circuit
13.6.6
How is a null modem cable identified:
(a)
Direct connection between all the signal lines
(b)
No connections to TD and RD lines
(c)
Cross-over between the TD and RD, and handshaking lines
(d)
No hardware handshaking lines
13.6.7
How is a modem cable identified:
(a)
Direct connection between all the signal lines
