lord loh.
Member
Here is an old reference of my EPROM question
The EPROM programmer that I am designing has got two modes. viz Read / Programme.
The read mode has the following requirements:
Vcc=5v
Vpp=5v (programming voltage)
The programming mode has the following requirements:
Vcc=6v
Vpp=12v
The datasheet of the EPROM in question(M27256 8Kb) instructs that the Vpp be applied simultaneously or after Vcc. The VIL=Vss-0.1v and VIH=Vcc+1v
The solution I see to the problem is by using a 555 to provide the Vpp a short time (delayed start) after the switch is moved from the Read<->Prog. mode.
In the mean time the data and address from the counter shall be on the respective buses of the ROM. Can this potentially damage the ROM? ie. Supplying signals without the Vcc and Vpp. (I read that is is true for op-amps). Is the given protection circuit any good?
Could using a delayed start Vss be a solution? I guess not.
Can anyone please help me with my power supply unit....
Any tips or sample circuits will guide me.
Thank you.
The EPROM programmer that I am designing has got two modes. viz Read / Programme.
The read mode has the following requirements:
Vcc=5v
Vpp=5v (programming voltage)
The programming mode has the following requirements:
Vcc=6v
Vpp=12v
The datasheet of the EPROM in question(M27256 8Kb) instructs that the Vpp be applied simultaneously or after Vcc. The VIL=Vss-0.1v and VIH=Vcc+1v
The solution I see to the problem is by using a 555 to provide the Vpp a short time (delayed start) after the switch is moved from the Read<->Prog. mode.
In the mean time the data and address from the counter shall be on the respective buses of the ROM. Can this potentially damage the ROM? ie. Supplying signals without the Vcc and Vpp. (I read that is is true for op-amps). Is the given protection circuit any good?
Could using a delayed start Vss be a solution? I guess not.
Can anyone please help me with my power supply unit....
Any tips or sample circuits will guide me.
Thank you.
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