
000-0046140-111
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SLG46140
22.2 POR Sequence
The POR system generates a sequence of signals that enable certain macrocells. The sequence is shown in
As can be seen from
after the VDD has start ramping up and crosses the Power_ON threshold, first, the on-chip NVM
memory is reset. Next, the chip reads the data from NVM, and transfers this information to SRAM registers that serve to configure
each macrocell, and the Connection Matrix which routes signals between macrocells. The third stage causes the reset of the input
pins, and then to enable them. After that, the LUTs are reset and become active. After LUTs the Delay cells, RC OSC, DFFs,
Latches and Pipe Delay are initialized. Only after all macrocells are initialized internal POR signal (POR macrocell output) goes
from LOW to HIGH. The last portion of the device to be initialized are the output PINs, which transit from high impedance to active
at this point.
The typical time that takes to complete the POR sequence varies by device type in the GreenPAK family. It also depends on many
environmental factors, such as: slew rate, VDD value, temperature and even will vary from chip to chip (process influence).
Figure 93. POR sequence
VDD
POR_NVM
(reset for NVM)
NVM_ready_out
POR_GPI
(reset for input enable)
POR_LUT
(reset for LUT output)
POR_CORE
(reset for DLY/RCO/DFF
/Latch/Pipe DLY
POR_OUT
(generate low to high to matrix)
POR_GPO
(reset for output enable)
t
t
t
t
t
t
t
t