| 摘要 |
A multi-level pattern for testing e.g. an input output circuit is generated from a pseudo random binary sequence (PRBS). A non-return to zero (NRZ) PRBS signal TP is generated by a PRBS generator 21 and provided to a bit detector 22 to create two trigger outputs T1, T2. The trigger outputs control first and second state machines 23, 24 each producing an output O1, O2 consisting of a pseudo-random voltage. One state machine produces negative voltages and the other state machine produces positive voltages. The outputs are combined in a combiner 27 to give a multi-level output CO which is provided to a transmission channel 3. The multi-level output is therefore created from the PRBS by mapping bits from the binary signal onto symbols of the multi-level output (see figure 2). |
