PSD4235G2-90UI STMicroelectronics, PSD4235G2-90UI Datasheet - Page 44

• 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

Programming Flash memory
9.2
44/129
Figure 5.
Data toggle
Checking the Toggle Flag bit (DQ6/DQ14) is another method of determining whether a
Program or Erase cycle is in progress or has completed.
algorithm.
When the MCU issues a Program instruction, the embedded algorithm within the PSD
begins. The MCU then reads the location to be programmed in Flash memory to check the
status. The Toggle Flag bit (DQ6/DQ14) toggles each time the MCU reads this location until
the embedded algorithm is complete. The MCU continues to read this location, checking the
Toggle Flag bit (DQ6/DQ14) and monitoring the Error Flag bit (DQ5/DQ13). When the
Toggle Flag bit (DQ6/DQ14) stops toggling (two consecutive READs yield the same value),
and the Error Flag bit (DQ5/DQ13) remains 0, the embedded algorithm is complete. If the
Error Flag bit (DQ5/DQ13) is 1, the MCU should test the Toggle Flag bit (DQ6/DQ14) again,
Data polling flowchart
No
at Valid Even Address
READ DQ5 and DQ7
(DQ13 and DQ15)
Issue RESET
READ DQ7
Cycle failed
instruction
(Data15)
(Data15)
Program
or Erase
START
(DQ15)
(DQ13)
(DQ15)
(DQ15)
Data7
Data7
DQ7
DQ5
DQ7
= 1
=
=
No
Yes
No
Yes
Yes
complete
Program
or Erase
Cycle is
Figure 6
AI04920
shows the Data Toggle
PSD4235G2