WebEE

2732:
PIN 1 - not used.

PIN 20 - MODE B and MODE D are both low. U16:C pin 8 will remain low and U17:B pin 6 will follow PROG PULSE. U17:C pin 8 will therefore be PROG PULSE inverted, and is coupled via D6 to PIN 20. PIN 20 is only pulled up in Program mode, so in Read mode it is permanently low.

PIN 22 - MODE D and MODE C- are both low and MODE A is high, so U15:B pin 6 is high. This switches on Q1 and Q2, coupling VPP to PIN 22

PIN 23 - MODE D is low, so Q5 and Q6 remain off. A11 is coupled to PIN 23 via D4.

PIN 26 - as 2716.

PIN 27 - not used.

2764 and 27128:
PIN 1 - MODE A is high. This switches on Q3 and Q4, coupling VPP to PIN 1.

PIN 20 - MODE B is high and MODE C is low. U16:C pin 8 remains low and U17:B pin 6 remains high, therefore

U17:C pin 8 remains low.

PIN 22 - MODE A and MODE C- are both high, so U15:B pin 6 is low and Q1 and Q2 remain off. R-/W is coupled to PIN 22 by D2.

PIN 23 - as 2732.

PIN 26 - MODE C is low so Q7 and Q8 remain off. A13 is coupled to PIN 26 by D5. Note that in a 2764 EPROM there is no connection to PIN 26.

PIN 27 - MODE B is high and A14 will remain low since it is outside the addressing range. U17:D pin 11 will therefore follow PROG PULSE-.

27256:
PIN 1 - as 2764.

PIN 20 - as 2732.

PIN 22 - as 2764.

PIN 23 - as 2732.

PIN 26 - as 2764.

PIN 27 - MODE B is low so U16:D pin 11 will remain low. U17:D pin 11 will follow A14.