PSD813F2 datasheet(85/128 Pages) STMICROELECTRONICS

85 / 128 page

PSD8XXFX

Reset timing and device status at reset

Doc ID 7833 Rev 7

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Reset timing and device status at reset

18.1

Power-up reset

Upon Power-up, the PSD requires a Reset (RESET) pulse of duration tNLNH-PO after VCC is

steady. During this period, the device loads internal configurations, clears some of the

registers and sets the Flash memory into operating mode. After the rising edge of Reset

(RESET), the PSD remains in the Reset mode for an additional period, tOPR, before the first

memory access is allowed.

The Flash memory is reset to the READ mode upon Power-up. Sector Select (FS0-FS7 and

CSBOOT0-CSBOOT3) must all be low, Write Strobe (WR, CNTL0) high, during Power On

Reset for maximum security of the data contents and to remove the possibility of a byte

being written on the first edge of Write Strobe (WR, CNTL0). Any Flash memory WRITE

cycle initiation is prevented automatically when VCC is below VLKO.

18.2

Warm reset

Once the device is up and running, the device can be reset with a pulse of a much shorter

duration, tNLNH.

The same tOPR period is needed before the device is operational after warm reset.

Figure 33 shows the timing of the Power-up and warm reset.

18.3

I/O pin, register and PLD status at Reset

Table 34 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 PSDabel equations.

18.4

Reset of Flash memory erase and program cycles (on the

PSD834Fx)

A Reset (RESET) also resets the internal Flash memory state machine. During a Flash

memory program or erase cycle, Reset (RESET) terminates the cycle and returns the Flash

memory to the Read mode within a period of tNLNH-A.

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