Motorola MCF5281 用户手册

27-50

MOTOROLA

 

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.

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.

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.

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