MOTOROLA
Chapter 14. QADC64E Enhanced Mode Operation
14-11
Programming the QADC64E Registers
Depending on when the FREEZE signal is asserted, there are three possible queue "freeze"
scenarios:
When a queue is not executing, the QADC64E freezes immediately
When a queue is executing, the QADC64E completes the conversion in progress and
then freezes
If, during the execution of the current conversion, the queue operating mode for the
active queue is changed, or a queue 2 abort occurs, the QADC64E freezes
immediately
During freeze mode, both the analog clock, QCLK, and periodic/interval timer are held in
reset. When the QADC64E enters the freeze mode while a queue is active, the current CCW
location of the queue pointer is saved.
During freeze, the analog clock, QCLK, is held in reset and the periodic/interval timer is
held in reset. External trigger events that occur during the freeze mode are not captured. The
BIU remains active to allow IMB3 access to all QADC64E registers and RAM. Although
the QADC64E saves a pointer to the next CCW in the current queue, the software can force
the QADC64E to execute a different CCW by writing new queue operating modes for
normal operation. The QADC64E looks at the queue operating modes, the current queue
pointer, and any pending trigger events to decide which CCW to execute when exiting
freeze.
If the FRZ bit is clear, the internal FREEZE signal is ignored.
14.3.1.3 Switching Between Legacy and Enhanced Modes of Operation
The LOCK and FLIP bits of the QADCMCR register control the operating mode of the
QADC64E modules. Out of reset, the QADC64E modules are in legacy mode (FLIP = 0)
and the LOCK bit is clear, indicating that the module is locked in legacy mode. In order to
change the value of the FLIP bit, the operating mode must first be unlocked by setting the
LOCK bit. Only then can the FLIP bit be changed. Finally, the LOCK bit must be cleared
again to protect the state of the FLIP bit from future writes.
1. Write LOCK = 1 to unlock operating mode bit.
2. Modify the value of FLIP as required.
— FLIP = 0 legacy mode enabled
— FLIP = 1 enhanced mode enabled
3. Write LOCK = 0 and new FLIP bit value to preserve the value of FLIP bit
Example 1: switching from legacy mode to enhanced mode
— QADCMCR = 0x280; LOCK =1, SUPV = 1
— QADCMCR = 0x380; LOCK =1, write FLIP = 1, SUPV = 1
— QADCMCR = 0x180; LOCK = 0, FLIP = 1, SUPV = 1
Subsequent writes to the FLIP bit will have no effect while LOCK = 0.