PSD932F2-A-20UI Просмотр технического описания (PDF) - STMicroelectronics
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PSD932F2-A-20UI Datasheet PDF : 94 Pages
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Preliminary Information
PSD9XX Family
The
PSD9XX
Functional
Blocks
(cont.)
9.5.3 Reset and Power On Requirement
9.5.3.1 Power On Reset
Upon power up the PSD9XX requires a reset pulse of tNLNH-PO (minimum 1 ms) after
VCC is steady. During this time period the device loads internal configurations, clears
some of the registers and sets the Flash into operating mode. After the rising edge of
reset, the PSD9XX remains in the reset state for an additional tOPR (maximum 120 ns)
nanoseconds before the first memory access is allowed.
The PSD9XX Flash memory is reset to the read array mode upon power up. The FSi
and CSBOOTi select signals along with the write strobe signal must be in the false
state during power-up reset for maximum security of the data contents and to remove
the possibility of a byte being written on the first edge of a write strobe signal. Any Flash
memory write cycle initiation is prevented automatically when VCC is below VLKO.
9.5.3.2 Warm Reset
Once the device is up and running, the device can be reset with a much shorter pulse of
tNLNH (minimum 150 ns). The same tOPR time is needed before the device is operational
after warm reset. Figure 25 shows the timing of the power on and warm reset.
Figure 25. Power On and Warm Reset Timing
OPERATING LEVEL
VCC
RESET
t NLNH – PO
POWER ON RESET
t OPR
t NLNH
t NLNH-A
WARM t OPR
RESET
9.5.3.3 I/O Pin, Register and PLD Status at Reset
Table 33 shows the I/O pin, register and PLD status during power on reset, warm reset
and power down mode. PLD outputs are always valid during warm reset, and they are
valid in power on reset once the internal PSD configuration bits are loaded. This loading of
PSD is completed typically long before the VCC ramps up to operating level. Once the PLD
is active, the state of the outputs are determined by the PLD equations.
59
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