I/O processing 79 A B C D
(i) T (i) T (i) F (i) F
(ii) T (ii) F (ii) T (ii) F
6 Decide whether each of these statements is True (T) or False (F). For communications over distances of the order of 100 to 300 m with a high transmission rate: (i) The RS232 interface can be used. (ii) The 20 mA current loop can be used. A B C D 7
(i) T (i) T (i) F (i) F
(ii) T (ii) F (ii) T (ii) F
Decide whether each of these statements is True (T) or False (F). With input/output processing, mass input/output copying: (i) Scans all the inputs and copies their states into RAM. (ii) Is a faster process than continuous updating. A B C D
8
(ii) T (ii) F (ii) T (ii) F
The cycle time of a PLC is the time it takes to: A B C D
9
(i) T (i) T (i) F (i) F
Read an input signal. Read all the input signals. Check all the input signals against the program. Read all the inputs, run the program and update all outputs.
Decide whether each of these statements is True (T) or False (F). A PLC with a long cycle time is suitable for: (i) Short duration inputs. (ii) High frequency inputs. A B C D
(i) T (i) T (i) F (i) F
(ii) T (ii) F (ii) T (ii) F
10 Specify (a) the odd parity bit, (b) the even parity bit, to be used when the data 1010100 is transmitted. 11 Explain the purpose of using a parity bit. 12 Explain the continuous updating and the mass input/output copying methods of processing inputs/outputs.