
4/29/2020
Godson 3A2000 / 3B2000 Processor User Manual
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In order to more easily control the reset pin in STR and other states, you can use the reset_ctrl (0x150) register
For special reset pin (DDR_RESETn) control, there are two main control modes:
(1) In general mode, reset_ctrl [1: 0] == 2'b00. In this mode, the reset signal pin behaves as a
Compatible with general control modes. Connect DDR_RESETn directly to the corresponding pin on the memory slot on the motherboard. lead
The behavior of the feet is:
● When not powered: the pin status is low;
● At power-on: the pin status is low;
● When the controller starts to initialize, the pin state is high;
● During normal operation, the pin status is high.
The timing is shown below:
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Godson 3A2000 / 3B2000 Processor User Manual Part 1
Sys_reset
DDR_RESETn
Internal reset
POWER
Software enableDLL lock
Particle RESETn
(2) Reverse mode, reset_ctrl [1: 0] == 2'b10. In this mode, the reset signal pin is in memory
In actual control, the effective level is opposite to the general control mode. So on the motherboard
DDR_RESETn is connected to the corresponding pin on the memory slot through an inverter. The behavior of the pins is:
● When not powered: the pin status is low;
● At power-on: the pin status is low;
● When the controller starts to configure: the pin state is high;
● When the controller starts to initialize: the pin state is low;
● Normal operation: the pin status is low.
The timing is shown below:
Sys_reset
DDR_RESETn
Internal reset
POWER
Software enableDLL lock
Particle RESETn
(3) Reset inhibit mode, pm_reset_ctrl [1: 0] == 2'b01. In this mode, the reset signal pin
During the work of a memory, keep low level. Therefore, the motherboard needs to pass DDR_RESETn through the inverter and the memory
The corresponding pins on the slot are connected. The behavior of the pins is: