QADC64E Enhanced Mode Operation
MPC561/MPC563 Reference Manual, Rev. 1.2
Freescale Semiconductor
14-49
WARNING
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 14-23. QADC64E Clock Subsystem Functions
The MCU system clock frequency (IMB3 system clock – f
SYSCLK
) is the basis of the QADC64E timing.
QCLK is generated by a software selectable prescaler that divides f
SYSCLK
thus allowing the A/D
conversion time to be maximized across f
SYSCLK
. The software establishes the frequency of QCLK
waveform by setting the PRESCALER field in the QACR0 register.
When the value of PRESCALER > 0 the resulting frequency of QCLK is calculated using the following
formula:
f
QCLK
= f
SYSCLK
/ (PRE 1)
The QADC64E requires that f
SYSCLK
be at least twice f
QCLK
. Therefore if the value in the PRESCALER
field is set to Zero, the resulting QCLK frequency is calculated to be:
f
QCLK
= f
SYSCLK
/ 2
QADC CLOCK BLOCK
Prescaler Rate Selection
(from Control Register 0)
Binary Counter
Periodic / interval
Timer Select
215
214
213
212
211
210
29
28
27
216 217
Clock
Generate
QCLK
QADC Clock
( F
SYS
/ ÷2 to F
SYS
/ ÷40 )
Input Sample Time
QUEUE 1 & 2 Timer
SAR Control
SAR[9:0]
Periodic/interval
Trigger Event
System Clock (F
SYS
)
A/D Converter
State Machine
for Q1 and Q2
2
8
(From CCW)
Mode Rate Selection
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...