M9346-RDS3T datasheet(5/34 Pages) STMICROELECTRONICS

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M93S66, M93S56, M93S46

An internal Power-on Data Protection mechanism

in the M93Sx6 inhibits the device when the supply

is too low.

POWER-ON DATA PROTECTION

To prevent data corruption and inadvertent write

operations during power-up, a Power-On Reset

(POR) circuit resets all internal programming cir-

cuitry, and sets the device in the Write Disable

mode.

–

At Power-up and Power-down, the device

must not be selected (that is, Chip Select Input

(S) must be driven Low) until the supply

voltage reaches the operating value VCC

specified in Table 5. to Table 6..

–

When VCC reaches its valid level, the device is

properly reset (in the Write Disable mode) and

is ready to decode and execute incoming

instructions.

For the M93Sx6 devices (5V range) the POR

threshold voltage is around 3V. For the M93Sx6-

W (3V range) and M93Sx6-R (2V range) the POR

threshold voltage is around 1.5V.

INSTRUCTIONS

The instruction set of the M93Sx6 devices con-

tains seven instructions, as summarized in Table

2. to Table 3.. Each instruction consists of the fol-

lowing parts, as shown in Figure 4.:

■

Each instruction is preceded by a rising edge

on Chip Select Input (S) with Serial Clock (C)

being held Low.

■

A start bit, which is the first ‘1’ read on Serial

Data Input (D) during the rising edge of Serial

Clock (C).

■

Two op-code bits, read on Serial Data Input

(D) during the rising edge of Serial Clock (C).

(Some instructions also use the first two bits of

the address to define the op-code).

■

The address bits of the byte or word that is to

be accessed. For the M93S46, the address is

made up of 6 bits (see Table 2.). For the

M93S56 and M93S66, the address is made up

of 8 bits (see Table 3.).

The M93Sx6 devices are fabricated in CMOS

technology and are therefore able to run as slow

as 0 Hz (static input signals) or as fast as the max-

imum ratings specified in Table 16. to Table 19..

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