
4/29/2020
Loongson 3A3000 / 3B3000 Processor User Manual
16
15
DO_TEST
pull up
1'b1 means function mode
1'b0 means test mode
ICCC_EN
drop down
1'b1 means multi-chip consistent interconnect mode
1'b0 means single chip mode
NODE_ID [1: 0]
Indicates the processor number in multi-chip consistent interconnect mode
CLKSEL [15: 0]
HT clock control
signal
effect
CLKSEL [15]
1'b1 means the HT controller frequency is only set by hardware
1'b0 means HT controller frequency can be set by software
CLKSEL [14]
1'b1 means HT PLL uses normal clock input
1'b0 means HT PLL uses differential clock input
CLKSEL [13:12]
2'b00 means the PHY clock is 1.6GHZ
2'b01 indicates that the PHY clock is 3.2GHZ
2'b10 means the PHY clock is 1.2GHz
2'b11 means the PHY clock is 2.4GHz
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Godson 3A3000 / 3B3000 Processor User Manual • Volume 1
CLKSEL [11:10]
2'b00 indicates that the HT controller clock is divided by 8 of the PHY clock
2'b01 indicates that the HT controller clock is divided by 4 of the PHY clock
2'b10 means the HT controller clock is divided by 2 of the PHY clock
2'b11 indicates that the HT controller clock is SYSCLOCK
Note: When CLKSEL [13:10] == 4'b1111, the HT controller clock is in bypass mode and used directly
External input 100MHz reference clock
MEM clock control
signal
effect
CLKSEL [9: 5]
5'b11111 means MEM clock directly uses memclk
5'b01111 indicates that the MEM clock is set by software. For the setting method, see
Section 2.6
In other cases, the MEM clock is
memclk * (clksel [8: 5] +30) / (clksel [9] +3)
Note:
memclk * (clksel [8: 5] +30) must be 1.2GHz ~ 3.2GHz
memclk is the input reference clock, which must be 20 ~ 40MHz
CORE clock control
signal
effect
CLKSEL [4: 0]
5'b11111 indicates that the CORE clock directly uses sysclk
5'b011xx indicates that the CORE clock is set by software. For the setting method, see
Instructions in Section 2.6.
5'b01111 is normal working mode, otherwise it is debugging mode
5'b0110x indicates that the processor interface is in asynchronous mode
5'b011x0 means delayed debug control mode
In other cases, the CORE clock is
sysclk * (clksel [3: 0] +30) / (clksel [4] +1)
Note: