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Godson 3A2000 / 3B2000 Processor User Manual
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The method of using the CLKSEL pin configuration is relatively simple and will not be described here. Use software register to set
Method
.28 section specifically noted, this in addition to some of the places that require special attention be specified.
When splitting a 16-bit HT into two 8-bit uses, only the software frequency configuration register of HT LO can
PLL and bus frequency division control, including HT HI bus frequency division value. In other words, if no treatment is taken, when HT
Resetting the frequency by LO will also cause the frequency of HT HI to change. At this time, if HT HI is in normal work
In the enabled state, the bus may be unstable.
To avoid this situation, there are two methods that can be used.
The first is to connect the reset signals of all HT together, so that the software frequency of all HT controllers is configured
After the register configuration is completed, pull the HT reset signal low, and then pull high to re-shake. This will make HT LO
Switch the clock at the same time as HT HI to ensure the normal operation of the system. This method is suitable for four-way interconnection
HT0 connection in the system.
The other is when the reset signal of HT cannot be connected together. At this time, it needs to be prevented by software control
HT LO affects HT HI when switching the PLL frequency. The most direct way is to first set HT HI to reset state,
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Until HT LO finishes switching the PLL frequency, then reset the HT HI bus. This method is suitable for HT1 LO
Connect the bridge, HT1 HI cross interconnection.
10.8 HyperTransport multiprocessor support
Loongson No. 3 processor uses HyperTransport interface for multi-processor interconnection and can be automatically maintained by hardware
Consistency request between 4 chips. The following provides two multiprocessor interconnection methods:
Four piece Loongson No. 3 interconnection structure
The four CPUs are connected in pairs to form a ring structure. Each CPU uses two 8-bit controllers of HT0
Connected, where HTx_LO is the master device and HTx_HI is the slave device, and the interconnection structure as shown below is obtained
Figure 10-2 Four-piece Loongson No. 3 interconnection structure
Loongson 3 interconnection routing
Loongson No. 3 interconnection routing adopts simple XY routing method. When routing, X followed by Y, taking four chips as an example, ID
CPU0
HT0_
HI
HT0_
LO
HT
1
CPU1
HT0_
HI
HT0_
LO
CPU3
HT0_
HI
HT0_
LO
CPU2
HT0_
HI
HT0_
LO
8-bit HT bus
8 bit
H
T total
line
8-bit HT bus
8 bit
H
T total
line
IO
16-bit HT bus