Digital Control Subsystem

27.8.3 Scan Modes

The QADC queuing mechanism allows application software to utilize different requirements for automatically scanning input channels.

In single-scan mode, a single pass through a sequence of conversions defined by a queue is performed. In continuous-scan mode, multiple passes through a sequence of conversions defined by a queue are executed.

The possible modes are:

Disabled mode and reserved mode

Software-initiated single-scan mode

Externally triggered single-scan mode

Externally gated single-scan mode

Interval timer single-scan mode

Software-initiated continuous-scan mode

Externally triggered continuous-scan mode

Externally gated continuous-scan mode

Periodic timer continuous-scan mode

The following paragraphs describe single-scan and continuous-scan operations.

27.8.4 Disabled Mode

When disabled mode is selected, the queue is not active. Trigger events cannot initiate queue execution. When both queue 1 and queue 2 are disabled, there is no possibility of encountering wait states when accessing CCW table and result RAM. When both queues are disabled, it is safe to change the QCLK prescaler values.

27.8.5 Reserved Mode

Reserved mode is available for future mode definitions. When reserved mode is selected, the queue is not active. The behavior is the same as disabled mode.

27.8.6 Single-Scan Modes

A single-scan queue operating mode is used to execute a single pass through a sequence of conversions defined by a queue. By programming the MQ1 field in QACR1 or the MQ2 field in QACR2, these modes can be selected:

Software-initiated single-scan mode

Externally triggered single-scan mode

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MCF5282 User’s Manual

MOTOROLA

Page 634
Image 634
Motorola MCF5282, MCF5281 user manual Disabled Mode, Reserved Mode, Single-Scan Modes