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UG-1262
Rev. B | Page 19 of 312
CLOCK DIVIDERS REGISTER
Address: 0x4004C304, Reset: 0x00100404, Name: CTL1
The clock dividers register is used to set the divide rates for the HCLK, PCLK, and ACLK dividers. This register can be written to at any
time. All unused bits are read only, returning a value of 0. Writing to unused bits has no effect.
Table 8. Bit Descriptions for CTL1
Bits
Bit
Name
Settings Description
Reset Access
[31:24] Reserved
Reserved.
0x0 R
[23:16] ACLKDIVCNT
ACLK Clock Divider. This bit determines the ACLK rate based on the equation
ACLK = root clock/ACLKDIVCNT. For example, if the root clock is 26 MHz and
ACLKDIVCNT = 0x1, ACLK operates at 26 MHz. The value of ACLKDIVCNT takes
effect after a write access to this register and typically takes one ACLK cycle. This
register can be read at any time and can be written to at any time. The value
range is from 1 to 32. Values larger than 32 are saturated to 32. Value 0 and
Value 1 have the same results as divide by 1. The default value of this register is
configured such that ACLK = 1.625 MHz.
0x10 R/W
[15:14] Reserved
Reserved.
0x0 R
[13:8] PCLKDIVCNT
PCLK Clock Divider. Determines the PCLK rate based on the equation PCLK = root
clock/PCLKDIVCNT. For example, if the root clock is 26 MHz and PCLKDIVCNT = 0x2,
PCLK operates at 13 MHz. The value of PCLKDIVCNT takes effect after a write access
to this register and typically takes 2 to 4 PCLK cycles. This register can be read at
any time and can be written to at any time. The value range is from 1 to 32.
Values larger than 32 are saturated to 32. Value 0 and Value 1 have the same
results as divide by 1. The default value of this register is configured such that
PCLK frequency = 6.5 MHz. It is recommended to only use the 0x1, 0x2, or 0x4
value and matching PCLKDIVCNT with HCLKDIVCNT.
0x4 R/W
[7:6] Reserved
Reserved.
0x0 R
[5:0] HCLKDIVCNT
HCLK Divide Count. Determines the HCLK rate based on the equation: HCLK = root
clock/HCLKDIVCNT. For example, if the root clock is 26 MHz and HCLKDIVCNT = 0x1,
HCLK operates at 26 MHz. The value of HCLKDIVCNT takes effect after a write
access to this register and typically takes 2 to 4 PCLK cycles (not HCLK cycles).
This register can be read at any time and can be written to at any time. The
value range is from 1 to 32. Values larger than 32 are saturated to 32. Value 0
and Value 1 have the same results as divide by 1. The default value of this
register is configured such that HCLK = 6.5 MHz. It is recommended to only use
the values 0x1, 0x2, or 0x4 and match HCLKDIVCNT with PCLKDIVCNT.
0x4 R/W
USER CLOCK GATING CONTROL REGISTER
Address: 0x4004C314, Reset: 0x0000001F, Name: CTL5
User clock gating control is used to control the clock gating to peripherals.
Table 9. Bit Descriptions for CTL5
Bits Bit
Name
Settings Description
Reset Access
[31:6] Reserved
Reserved.
0x0 R
5 PERCLKOFF
Peripheral Clocks Off. This bit is used to disable all clocks connected to all
peripherals. After setting this bit, any read or write to any of the peripheral
registers automatically resets PERCLKOFF to 0, and that read or write transaction is
honored. After setting PERCLKOFF = 1, if the user reads the CTL5 register,
PERCLKOFF is automatically cleared and PERCLKOFF reads as 0. The user must
ensure that DMA transactions are done and no more transactions are expected
from the DMA. Ensure that the PERCLKOFF bit write is the last write and no writes
or reads to any of peripheral registers are performed after setting this bit.
Otherwise, the PERCLKOFF bit clears.
0x0 R/W
0
Clocks to all peripherals are active.
1
Clocks to all peripherals are gated off.