Signals

27.4.2.2Port QB Digital I/O Signals

Port QB signals are referred to as PQB[3:0] when used as a 4-bit digital input/output port. In addition to functioning as analog input signals, the port QB signals are also connected to the input of a synchronizer during reads and may be used as general-purpose digital inputs when the applied voltages meet VIH and VIL requirements.

Each port QB signal is configured as an input or output by programming the port data direction register (DDRQB). The digital input signal states are read from the port QB data register (PORTQB) when DDRQB specifies that the signals are inputs. The digital data in PORTQB is driven onto the port QB signals when the corresponding bits in DDRQB specify output. See Section 27.6.4.

27.4.3 External Trigger Input Signals

The QADC has two external trigger signals, ETRIG2 and ETRIG1. Each external trigger input is associated with one of the scan queues, queue 1 or queue 2. The assignment of ETRIG[2:1] to a queue is made by the TRG bit in QADC control register 0 (QACR0). When TRG = 0, ETRIG1 triggers queue 1 and ETRIG2 triggers queue 2. When TRG = 1, ETRIG1 triggers queue 2 and ETRIG2 triggers queue 1. See Section 27.6.5 “Control Registers.”

27.4.4 Multiplexed Address Output Signals

In non-multiplexed mode, the QADC analog input signals are connected to an internal multiplexer which routes the analog signals into the internal A/D converter.

In externally multiplexed mode, the QADC allows automatic channel selection through up to four external 4-to-1 multiplexer chips. The QADC provides a 2-bit multiplexed address output to the external multiplexer chips to allow selection of one of four inputs. The multiplexed address output signals, MA1 and MA0, can be used as multiplexed address output bits or as general-purpose I/O when external multiplexed mode is not being used.

MA[1:0] are used as the address inputs for up to four 4-channel multiplexer chips. Because the MA[1:0] signals are digital outputs in multiplexed mode, the state of their corresponding data direction bits in DDRQA is ignored.

27.4.5 Multiplexed Analog Input Signals

In external multiplexed mode, four of the port QB signals are redefined so that each represent four analog input channels. See Table 27-1.

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MCF5282 User’s Manual

MOTOROLA

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Motorola MCF5282 External Trigger Input Signals, Multiplexed Address Output Signals, Multiplexed Analog Input Signals