M93S46 ST Microelectronics, M93S46 Datasheet - Page 13

• Manufacturer Part Number: M93S46
• Description: 4Kbit / 2Kbit and 1Kbit 16-bit wide MICROWIRE Serial Access EEPROM with Block Protection
• Manufacturer: ST Microelectronics

ing the Protection Register Write (PRWRITE) in-
struction. When the OTP bit is set, the Ready/Busy
status cannot appear on Serial Data Output (Q).
When the OTP bit is not set, the Busy status ap-
pears on Serial Data Output (Q).
Note: A Protection Register Enable (PREN) in-
struction must immediately precede the Protection
Register Disable (PRDS) instruction.
Figure 8. Write Sequence with One Clock Glitch
CLOCK PULSE COUNTER
In a noisy environment, the number of pulses re-
ceived on Serial Clock (C) may be greater than the
number delivered by the Bus Master (the micro-
controller). This can lead to a misalignment of the
instruction of one or more bits (as shown in Figure
8) and may lead to the writing of erroneous data at
an erroneous address.
To combat this problem, the M93Sx6 has an on-
chip counter that counts the clock pulses from the
start bit until the falling edge of the Chip Select In-
put (S). If the number of clock pulses received is
not the number expected, the WRITE, PAWRITE,
WRALL, PRWRITE or PRCLEAR instruction is
S
D
C
START
"0"
WRITE
"1"
An
Glitch
An-1
COMMON I/O OPERATION
Serial Data Output (Q) and Serial Data Input (D)
can be connected together, through a current lim-
iting resistor, to form a common, single-wire data
bus. Some precautions must be taken when oper-
ating the memory in this way, mostly to prevent a
short circuit current from flowing when the last ad-
dress bit (A0) clashes with the first data bit on Se-
rial Data Output (Q). Please see the application
note AN394 for details.
aborted, and the contents of the memory are not
modified.
The number of clock cycles expected for each in-
struction, and for each member of the M93Sx6
family, are summarized in Table 2 to Table 3. For
example, a Write Data to Memory (WRITE) in-
struction on the M93S56 (or M93S66) expects 27
clock cycles from the start bit to the falling edge of
Chip Select Input (S). That is:
ARE SHIFTED BY ONE BIT
ADDRESS AND DATA
1 Start bit
+ 2 Op-code bits
+ 8 Address bits
+ 16 Data bits
An-2
M93S66, M93S56, M93S46
D0
AI01395
13/32