Electrical symbols, what does a dot before a triangle mean?
Just another way of drawing a logic inverter ("NOT").

The triangle-with-bubble is an inverter: logic high input yields logic low output, and vice versa. Usually the bubble is shown on the output, but in a mixed-logic system, the bubble can be shown on the input instead.

When the bubble is on the input instead of the output, that indicates that the input is an active-low input.