Hello, I find different datasheets for the 74ls240 chip.
The differences are in the enable inputs, in some datasheets (eg motorola) one of the two inputs are non inverted, whereas in some other both are inverted.
In the datasheets that one of the two is non-inverted, the truth table does not cope with it.
Please advise me which one is correct.
Wrong symbol in the Motorola datasheet. Better refer to a datasheet from an active product/manufacturer (e.g. Fairchild, TI) that can be expected to undergo periodical error corrections.