QADC64E Legacy Mode Operation
MPC561/MPC563 Reference Manual, Rev. 1.2
13-48
Freescale Semiconductor
NOTE
A change in the prescaler value while a conversion is in progress is likely to
corrupt the result from any conversion in progress. Therefore, any prescaler
write operation should be done only when both queues are in the disabled
modes.
Figure 13-24. QADC64E Clock Subsystem Functions
To accommodate wide variations of the main MCU clock frequency (IMB3 clock — f
SYS
), QCLK is
generated by a programmable prescaler which divides the MCU IMB3 clock to a frequency within the
specified QCLK tolerance range. To allow the A/D conversion time to be maximized across the spectrum
of IMB3 clock frequencies, the QADC64E prescaler permits the frequency of QCLK to be software
selectable. It also allows the duty cycle of the QCLK waveform to be programmable.
The software establishes the basic high phase of the QCLK waveform with the PSH (prescaler clock high
time) field in QACR0, and selects the basic low phase of QCLK with the prescaler clock low time (PSL)
field. The combination of the PSH and PSL parameters establishes the frequency of the QCLK.
Prescaler Rate Selection
(From Control Register 0):
Binary Counter
PERIODIC/INTERVAL
Timer Select
215
214
213
212
211
210
29
28
27
216217
One’s Complement
Compare
Clock
Generate
5-Bit
Down Counter
Zero
Detect
Reset QCLK
Load PSH
Set QCLK
QCLK
QADC64E Clock
(F
SYS
/ 2 to F
SYS
//40 )
Low Time
High Time
Input Sample Time
Queue 1 & 2 Timer
SAR Control
SAR
Periodic / Interval
Trigger Event
5
3
3
5
IMB3 Clock
A/D Converter
State Machine
for Q1 AND Q2
2
8
10
Mode Rate Selection
from (CCW)
Cycles (PSL)
Cycles (PSH)
(F
SYS
)
2
Summary of Contents for MPC561
Page 84: ...MPC561 MPC563 Reference Manual Rev 1 2 lxxxiv Freescale Semiconductor...
Page 144: ...Signal Descriptions MPC561 MPC563 Reference Manual Rev 1 2 2 46 Freescale Semiconductor...
Page 206: ...Central Processing Unit MPC561 MPC563 Reference Manual Rev 1 2 3 62 Freescale Semiconductor...
Page 302: ...Reset MPC561 MPC563 Reference Manual Rev 1 2 7 14 Freescale Semiconductor...
Page 854: ...Time Processor Unit 3 MPC561 MPC563 Reference Manual Rev 1 2 19 24 Freescale Semiconductor...
Page 968: ...Development Support MPC561 MPC563 Reference Manual Rev 1 2 23 54 Freescale Semiconductor...
Page 1144: ...Internal Memory Map MPC561 MPC563 Reference Manual Rev 1 2 B 34 Freescale Semiconductor...
Page 1212: ...TPU3 ROM Functions MPC561 MPC563 Reference Manual Rev 1 2 D 60 Freescale Semiconductor...
Page 1216: ...Memory Access Timing MPC561 MPC563 Reference Manual Rev 1 2 E 4 Freescale Semiconductor...
