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MAX32660 User Guide
Maxim Integrated
Page 25 of 195
SYSCLK drives the Arm® Cortex-M4 with FPU and is used to generate the following internal clocks:
•
Advanced High-Performance Bus (AHB) Clock
−
𝐻𝐶𝐿𝐾 = 𝑆𝑌𝑆𝐶𝐿𝐾
•
Advanced Peripheral Bus (APB) Clock,
−
𝑃𝐶𝐿𝐾 =
𝑆𝑌𝑆𝐶𝐿𝐾
2
The Real-Time Clock (RTC) uses the 32.768kHz oscillator for its clock source.
All oscillators are reset to their POR reset default state during a Power-On Reset, System Reset and a Watchdog Reset.
Oscillator settings are not reset during a Soft Reset or Peripheral Reset.
sh ws ach scillat r’s nabl stat f r
each type of reset source in the MAX32660.
details the effect each reset source has on the System Clock selection
and the System Clock prescaler settings.
Table 4-3: Reset Sources and Effect on Oscillator Status
Reset Source
Oscillator
POR
System
Watchdog
Soft
Peripheral
HFIO
Enabled
Enabled
Enabled
Retains State Retains State
8kHz nano-ring
Enabled
Enabled
Enabled
Enabled
Enabled
32kHz oscillator
Disabled Retains State Retains State Retains State Retains State
Table 4-4: Reset Sources and Effect on System Oscillator Selection and Prescaler
Reset Source
Clock Field
POR
System
Watchdog
Soft
Peripheral
System Oscillator
clksel
0 (HFIO)
0 (HFIO)
0 (HFIO)
Retains State Retains State
System Clock Prescaler
psc
1
1
1
Retains State Retains State
4.3
Oscillator Sources and System Clock Selection
Before using any oscillator, the oscillator must first be enabled by setting its corresponding enable bit in the System Clock
Control Register,
. Before setting any oscillator as SYSOSC, its corresponding oscillator ready bit in the
register must first be checked.
Once the corresponding oscillator ready bit is set, the oscillator can then be selected as SYSOSC by configuring the Clock
Source Select field (
clksel
. f an scillat r’s r a y bit r a s 0, th har war s n t all w s l cting th
oscillator as the SYSOSC.
Any time firmware changes SYSOSC by changing
clksel
, the Clock Ready bit,
.clkrdy,
is
automatically cleared to indicate that a SYSOSC switchover is in progress. The application should read the clock ready field
until it returns 1. While the clock ready field reads 0, the prior clock is used as the SYSOSC.
Immediately before entering any low-power mode the application must enable any oscillator needed during the low power
mode.
Refer to
for details on reset sources and effects on each of the oscillators described below.
Содержание MAX32660
Страница 4: ...MAX32660 User Guide Maxim Integrated Page 4 of 195 8 UART 84 9 Real Time Clock RTC 96 10 Timers 105...
Страница 7: ...MAX32660 User Guide Maxim Integrated Page 7 of 195 15 Trademarks 195 16 Revision History 195...
Страница 14: ...MAX32660 User Guide Maxim Integrated Page 14 of 195 Figure 2 1 MAX32660 High Level Block Diagram...