AT90PWM81 View Datasheet(PDF) - Atmel Corporation
Part Name
Description
MFG CO.
'AT90PWM81' PDF : 325 Pages View PDF
AT90PWM81/161
5.5.6
the clock frequency and, of course, if the clock is alive. The user’s has itself to do the difference
between ‘no_clock_signal’ and ‘clock_signal_not_yet_available’.
• Bits 3:0 – CLKC3:0: Clock Control Bits 3 - 0
These bits define the command to provide to the ‘Clock Switch’ module. The special write
procedure must be followed to change the CLKC bits (see “Bit 7 – CLKCCE: Clock Control Change
Enable” on page 42).
1. Write the Clock Control Change Enable (CLKCCE) bit to one and all other bits in
CLKCSR to zero.
2. Within four cycles, write the desired value to CLKCSR register while clearing CLKCCE
bit.
Interrupts should be disabled when setting CLKCSR register in order not to disturb the
procedure.
Table 5-12. Clock command list.
Clock command
No command
Disable clock source
Enable clock source
Request for clock availability
Clock source switch
Recover system clock source code
CKOUT command
No command
CLKC3..0
0000 b
0001 b
0010 b
0011 b
0100 b
0101 b
0111 b
1xxx b
CLKSELR - Clock Selection Register
Bit
7
6
5
4
3
2
1
0
-
COUT
CSUT1 CSUT0 CSEL3 CSEL2 CSEL1 CSEL0 CLKSELR
Read/Write
R
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
CKOUT
fuse
SUT1..0
fuses
CKSEL3..0
fuses
• Bit 7– Res: Reserved Bit
This bit is reserved bit in the AT90PWM81/161 and will always read as zero.
• Bit 6 – COUT: Clock Out
The COUT bit is initialized with CKOUT Fuse bit.
The COUT bit is only used in case of ‘CKOUT’ command. Refer to Section 5.2.7 ”Clock Output
Buffer” on page 34 for using.
In case of ‘Recover System Clock Source’ command, COUT it is not affected (no recovering of
this setting).
• Bits 5:4 – CSUT1:0: Clock Start-up Time
CSUT bits are initialized with the values of SUT Fuse bits.
In case of ‘Enable/Disable Clock Source’ command, CSUT field provides the code of the clock
start-up time. Refer to subdivisions of Section 5.2 ”Clock Sources” on page 28 for code of clock
43
7734Q–AVR–02/12
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