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Basic Information
Question 1
What's the difference between the HT24LC and HT93LC Serial EEPROM series?
Answer
| Feature |
2-Wire (HT24LCxx) |
3-Wire (HT93LCxx) |
| Interface |
Serial data I/O、Clock |
Data in、Data out、Clock、CS |
| Clock Rate (max) |
400K |
2M |
| Page Write |
Yes |
No |
| Memory Organization |
X8 bit |
X8 bit or x16 bit |
| Write to All mode |
No |
Yes |
| Specific features |
Hardware write protect WP pin |
Software write protect EWDS instruction |
Question 2
What are the differences between the two A and B type packages in the HT93LC series of EEPROMs? What specific points should be noted when implementing read and write operations?Answer
The only differences are in the pin positions, the MCU read and write software for the two packages is the same.
Application Description
Question 1
How do I reset the HT93LCXX IC?
Answer
You can toggle CS pin Low again to reset the HT93LCXX.
Question 2
I'm trying to put an HT93LCXX IC in my circuit. There seems no fault for the read action, but data just can't be written in. What problem will that be?
Answer
It usually happens when issuing the write instruction, the correct number of bytes are not provided before the CS pin sets to low or the CS hasn't been set to low. Data writing will be activated on the falling edge of CS.
Question 3
When I issue a Write instruction to the HT93LCXX IC, what will happen if I give more or less clocks before setting the CS signal to Low ?
Answer
Because the write instruction will be activated on the falling edge of CS. If too many clocks than needed have been sent before the CS has been set to low, it will still function but the unnecessary clocks will be neglected. If the clocks are less then needed, the Write instruction will have no effect.
Question 4
Should I execute Toggle CS pin Low in between each instruction when I'm using an HT93LCXX? Answer
Yes, you have to toggle CS pin Low in between within each instruction, and the CS pulse should be at least 250ns. If you are executing the Write Command, you have to enable the Write Cycle by toggling CS pin Low. When the Write command is completed and you have detected a Ready signal, you have to toggle CS pin Low again before sending the next Start Bit.
Question 5
For HT93, between the issues of two different commands, is it necessary to pull low the CS pin?
Answer
Yes, and the low period of the CS pin should remain at least 250ns. If the operating voltage is 2.2V, the period should remain at least 1000ns. Note that in WRITE operation, after the completion of sending data, the CS pin should be pulled low for a period of time and then pulled high and wait for the HT93 acknowledging ready signal. Afterwards, the CS pin should be pulled low again before issuing the START bit of the next command, in other words, the CS pin should be pulled low twice.
Question 6
In the WRITE operation, can I use the DELAY method in stead of waiting for the READY signal from the DO pin?
Answer
You are not recommended to use the DELAY method mainly because only a READY signal on the DO pin indicates the completion of a WRITE command. Note that waiting for the READY signal on the DO pin might result in a dead loop if any failure happens. An additional time-out flag to prevent this situation is recommended. Anyway, if you have to use the DELAY for WRITE command, be sure to provide sufficient DELAY period, for the HT93 series, which should be at least 5ms.
Question 7
Why WRITE and ERASE command fail but other commands have no problem in using the HT93 EEPROM?
Answer
Note that for HT93 EEPROM READ, ERASE and WRITE commands, after writing the command code, address is not required, however, the DI pin should remain low, otherwise the command will be invalid. WRITE and ERASE commands fail but other commands pass, that is because the last bit of the READ command is 0 which cause the DI pin to remain low when the next clock comes. Precautions should be taken when using the WRITE and ERASE command.
Question 8
Why is it, that the data just written to the EEPROM, when read back, is missing or contains errors?
Answer
This is because the read instruction has not been used correctly. After a write instruction has been executed it is important to note the following. After the device has been selected using CS, and providing the clock on SK, then transmitting the write instruction code on DI along with the address and data and then deselecting the device, then the device must not be selected again until after the DS Deselect Time has elapsed. Additionally by examining the level on the DO pin, if there is a high level, then after the device has been deselected means that the data has been correctly written and verification completed, completing the full write operation. If the following chip select or deselect is missing, then the following write data operation will have errors. Therefore take note that after selecting the device with CS and issuing the clock on SK and reading the transmitted instruction code and address on DI, the DO pin at this time should show a low level. At this time SK should generate a high going edge after which the DO pin will transmit the data, which can be read out on successive transmitted SK signals. If the high going edge mentioned above is missing and the low level on the DO pin is read then the data will be read incorrectly.
Question 9
Why is it not possible to write data to the EEPROM?
Answer
The EEPROM has a write data protect function. After power on or after reception of a EWDS Erase/Write Disable instruction, any instructions pertaining to writing data to the EEPROM will have no effect on the EEPROM data. If it is required to write data to the EEPROM, then it is first necessary to execute an EWEN instruction. After the EEPROM receives the EWEN instruction, it will remain in permanent effect until power is removed or until an EWDS instruction is executed. In addition, when sending instructions, the EWDS and EWEN instructions must be executed according to the specification, otherwise the instructions will have no effect and any following on write instructions to the EEPROM will not be able to write data to the EEPROM.
Points to Note
Question 1
What are the steps to write data into an HT93LCXX?
Answer
After power-on, the HT93LCXX IC is default in EWDS (Erase/Write Disable) state, any data erasing or writing is invalid. Before writing data to the device, you have to issue the EWEN(Erase/Write Enable) instruction first. To prevent from false actions, you are recommended to send an EWDS command after the Write instruction is executed.
Question 2
Which writer should I use to program Holtek's EEPROM?
Answer
Please go to www.holtek.com.tw and choose Technical Support/Supporting Tools/Memory Programming where the relevant writer information that Holtek has certified is provided.
Question 3
If the EEPROM writer or version which I'm using now isn't on the list of your "Memory Programming" web page, how do I know if this writer can be used to program Holtek's EEPROM?
Answer
Only those writers and versions on the list on the "Memory Programming" page are certified by Holtek. For other writer information, please contact the
original manufacturers directly for further information.
Question 4
How can I program the EEPROM efficiently ?
Answer
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Make sure your writer and its software version support the item you want to program.
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Make sure the writer has passed self-test.
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Make sure the contact pins are clean and not oxidized.
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Do not touch the IC by hand.
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The operator, writer and the working table are grounded for all time.
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Make sure the contact between the IC and the pins is in good condition.
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Change the pin set after being used for some time.
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