(a) The table shows some data being transmitted with even parity. Complete the parity bit for each row and identify any rows with errors. Row D7 D6 D5 D4 D3...
Question 1 Report
(a) The table shows some data being transmitted with even parity. Complete the parity bit for each row and identify any rows with errors.
| Row | D7 | D6 | D5 | D4 | D3 | D2 | D1 | Expected parity | Received parity | Error? |
|---|---|---|---|---|---|---|---|---|---|---|
| 1 | 1 | 0 | 1 | 1 | 0 | 1 | 0 | 0 | ||
| 2 | 0 | 1 | 0 | 0 | 1 | 1 | 1 | 0 | ||
| 3 | 1 | 1 | 1 | 0 | 0 | 0 | 1 | 1 |
[4]
Answer Details
(a) The system uses even parity, so the expected parity bit should make the total count of 1-bits even. [4]
| Row | Data bits | Count of 1s in data | Expected parity | Received parity | Error? |
|---|---|---|---|---|---|
| 1 | 1 0 1 1 0 1 0 | 1+0+1+1+0+1+0 = 4 (even) | 0 | 0 | No error [1] |
| 2 | 0 1 0 0 1 1 1 | 0+1+0+0+1+1+1 = 4 (even) | 0 | 0 | No error [1] |
| 3 | 1 1 1 0 0 0 1 | 1+1+1+0+0+0+1 = 4 (even) | 0 | 1 | Yes, error detected [1] |
For Row 1, the data has four 1-bits (already even), so the expected parity bit is 0 and the received parity is 0: no error. For Row 2, the data again has four 1-bits, expected parity is 0, received is 0: no error. For Row 3, the data has four 1-bits, so the expected parity is 0, but the received parity is 1. The total (4 + 1 = 5) is odd, which violates even parity: error detected. [1]
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