27-40
MCF5282 User’s Manual
MOTOROLA
Digital Control Subsystem
27.8.1.2 Queue Priority Schemes
Because there are two conversion command queues and only one A/D converter, a priority
scheme determines which conversion occurs. Each queue has a variety of trigger events that
are intended to initiate conversions, and they can occur asynchronously in relation to each
other and other conversions in progress. For example, a queue can be idle awaiting a trigger
event; a trigger event can have occurred, but the first conversion has not started; a
conversion can be in progress; a pause condition can exist awaiting another trigger event to
continue the queue; and so on.
The following paragraphs and figures outline the prioritizing criteria used to determine
which conversion occurs in each overlap situation.
NOTE
Each situation in Figure 27-23 through Figure 27-33 is labeled
S1 through S19. In each diagram, time is shown increasing
from left to right. The execution of queue 1 and queue 2 (Q1
and Q2) is shown as a string of rectangles representing the
execution time of each CCW in the queue. In most of the
situations, there are four CCWs (labeled C1 to C4) in both
queue 1 and queue 2. In some of the situations, CCW C2 is
presumed to have the pause bit set, to show the similarities of
pause and end-of-queue as terminations of queue execution.
Trigger events are described in Table 27-22.
When a trigger event causes a CCW execution in progress to be aborted, the aborted
conversion is shown as a ragged end of a shortened CCW rectangle.
The situation diagrams also show when key status bits are set.
Table 27-23 describes the status bits.
Table 27-22. Trigger Events
Trigger
Events
T1
Events that trigger queue 1 execution (external trigger, software-initiated single-scan enable
bit, or completion of the previous continuous loop)
T2
Events that trigger queue 2 execution (external trigger, software-initiated single-scan enable
bit, timer period/interval expired, or completion of the previous continuous loop)
Table 27-23. Status Bits
Bit
Function
CF flag
Set when the end of the queue is reached
PF flag
Set when a queue completes execution up through a pause bit
Trigger overrun
error (TOR)
Set when a new trigger event occurs before the queue is finished servicing the
previous trigger event
Summary of Contents for ColdFire MCF5281
Page 124: ...3 20 MCF5282 User s Manual MOTOROLA EMAC Instruction Set Summary ...
Page 141: ...MOTOROLA Chapter 5 Static RAM SRAM 5 5 SRAM Programming Model ...
Page 142: ...5 6 MCF5282 User s Manual MOTOROLA SRAM Programming Model ...
Page 168: ...6 26 MCF5282 User s Manual MOTOROLA Interrupts ...
Page 186: ...7 18 MCF5282 User s Manual MOTOROLA Functional Description ...
Page 228: ...9 22 MCF5282 User s Manual MOTOROLA Functional Description ...
Page 246: ...10 18 MCF5282 User s Manual MOTOROLA Low Power Wakeup Operation ...
Page 254: ...11 8 MCF5282 User s Manual MOTOROLA Memory Map and Registers ...
Page 264: ...12 10 MCF5282 User s Manual MOTOROLA Chip Select Registers ...
Page 280: ...13 16 MCF5282 User s Manual MOTOROLA Misaligned Operands ...
Page 314: ...14 34 MCF5282 User s Manual MOTOROLA MCF5282 External Signals ...
Page 339: ...MOTOROLA Chapter 15 Synchronous DRAM Controller Module 15 25 SDRAM Example ...
Page 340: ...15 26 MCF5282 User s Manual MOTOROLA SDRAM Example ...
Page 356: ...16 16 MCF5282 User s Manual MOTOROLA DMA Controller Module Functional Description ...
Page 408: ...17 52 MCF5282 User s Manual MOTOROLA Buffer Descriptors ...
Page 446: ...20 24 MCF5282 User s Manual MOTOROLA Interrupts ...
Page 474: ...22 18 MCF5282 User s Manual MOTOROLA Programming Model ...
Page 510: ...23 36 MCF5282 User s Manual MOTOROLA Operation ...
Page 526: ...24 16 MCF5282 User s Manual MOTOROLA I2C Programming Examples ...
Page 672: ...28 12 MCF5282 User s Manual MOTOROLA Functional Description ...
Page 718: ...29 46 MCF5282 User s Manual MOTOROLA Motorola Recommended BDM Pinout ...
Page 750: ...32 8 MCF5282 User s Manual MOTOROLA Ordering Information ...