PSD4235G2-90UI STMicroelectronics, PSD4235G2-90UI Datasheet - Page 41

• Manufacturer Part Number: PSD4235G2-90UI
• Description: IC FLASH 4MBIT 90NS 80TQFP
• Manufacturer: STMicroelectronics

Specifications of PSD4235G2-90UI

• Format - Memory: FLASH
• Memory Type: FLASH
• Memory Size: 4M (512K x 8)
• Speed: 90ns
• Interface: Parallel
• Voltage - Supply: 4.5 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 80-TQFP, 80-VQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 497-1969

PSD4235G2
8.7
8.8
Table 30.
Table 31.
1. X = Not guaranteed value, can be read either 1 or 0.
2. DQ15-DQ0 represent the Data Bus bits, D15-D0.
3. FS0-FS7/CSBOOT0-CSBOOT3 are active high.
Data Polling (DQ7) - DQ15 for Motorola
When erasing or programming in Flash memory, the Data Polling bit (DQ7/DQ15) outputs
the complement of the bit being entered for programming/writing on the DQ7/DQ15 bit.
Once the Program instruction or the WRITE operation is completed, the true logic value is
read on the Data Polling bit (DQ7/DQ15, in a READ operation).
●
●
●
●
Toggle flag (DQ6) - DQ14 for Motorola
The PSD offers another way for determining when the Flash memory Program cycle is
completed. During the internal WRITE operation and when either FS0-FS7 or CSBOOT0-
CSBOOT3 is true, the Toggle Flag bit (DQ6/DQ14) bit toggles from 0 to ’1’ and 1 to ’0’ on
subsequent attempts to read any word of the memory.
When the internal cycle is complete, the toggling stops and the data read on the Data Bus
D0-D7 is the value from the addressed memory location. The device is now accessible for a
Polling
Polling
DQ15
DQ7
Data
Data
Data Polling is effective after the fourth WRITE pulse (for a Program instruction) or after
the sixth WRITE pulse (for an Erase instruction). It must be performed at the address
being programmed or at an address within the Flash memory sector being erased.
During an Erase cycle, the Data Polling bit (DQ7/DQ15) outputs a '0.' After completion
of the cycle, the Data Polling bit (DQ7/DQ15) outputs the last bit programmed (it is a ’1’
after erasing).
If the location to be programmed is in a protected Flash memory sector, the instruction
is ignored.
If all the Flash memory sectors to be erased are protected, the Data Polling bit
(DQ7/DQ15) is reset to ’0’ for about 100 µs, and then returns to the value from the
previously addressed location. No erasure is performed.
Status bits
Status bits for Motorola
Toggle
Toggle
DQ14
DQ6
Flag
Flag
Error Flag
Error Flag
DQ13
DQ5
DQ12
DQ4
(1)(2)(3)
X
X
timeout
timeout
Erase
DQ11
Erase
DQ3
DQ10
DQ2
X
X
DQ1
DQ9
X
X
Instructions
DQ0
DQ8
X
X
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