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P5040/P5020 Reference Design Board User Guide, Rev. 0
42
Freescale Semiconductor
Architecture
— Thus, COP directly controls the CPU_TRST.
Figure 19. P5040/P5020RDB Reset Hierarchy
5.5.1
System Reset Performed by the FPGA Reset Sequencer
The reference board FPGA contains a reset sequencer that properly manages the orderly bring-up of the
system. Note that this is not the same as the power sequencer, which is similar, but not specifically related
to reset.
After the system transitions to having fully-stable power supplies, the reset sequencer performs the
following:
1. Waits for all reset conditions to clear.
2. Configures and releases the processor from reset.
3. Idles waiting for further reset conditions to occur.
This table summarizes the reset conditions and actions of the FPGA.
Table 21. Reset Conditions and Actions of the FPGA Reset Sequencer
Signal
Type
Description
Action
HOT_RST_B
External HOT power stable
Restarts all FPGA internal state machines and registers
PWRGD
External 1U power stable
Causes full system reset unless the system is in S3 (power
down) state
ngPIXIS
PWRGD(SYSRST)
P5040/P5020
RRST
+
+
COP_TRST
GO
RESET
SEQ
PHY_RST
MEM_RST
GEN_RST
COP_HRST
HOTRST
RESET_REQ
wdog_rst
GO
RST
PORST
rreq_rst
COP_HRST
CPU_PORESET
TRST
CPU_TRST
HOTRST
Lower_case = internal signal
Upper case = external signal
+
XRST
ngPIXIS
No polarity information is shown
REGS
COP_SRST
CPU_HRESET
open drain