There is no need to use a DAC. Voltages are used to represent 1's and 0's by the convention that anything under 0.8V (AKA 'low') is a zero, and anything over 2.4V (AKA 'high') is a one. It's relatively simple to construct circuits that perform logic on these representative voltages.
For example, a circuit can output something in the 2.4V to 5V range to represent '1' if either input is over 2.4V, or something less than 0.8V otherwise, and you have an OR gate. If it requires both inputs representing 1 in order to output 2.4V, you have an AND gate. An inverter just outputs a high when the input is low, and vice-versa. You can build simple gates like these with just a very few transistors, and perform combinatorial boolean logic. By using groups of bits to represent numbers, you can even build circuits to add numbers with combinatorial logic, no software required.
Once you are working with gates, you can construct flip flops, and from them, registers and counters. Flip-flops allow you to store 1's and 0's from one point in time and use them later on. Registers and counters are circuits that perform functions on groups of bits that represent numbers. A register holds a number until you load a new number into it. A counter is like a register, but has another input that causes the stored number to increment. (Decrement is possible too). This puts you in the realm of state machines and sequential logic, still, no software required.
Memory systems are a way to store massive numbers of bits. At a component level, some memory is built like a huge collection of flip-flops, but more commonly there is another technology (DRAM) that, while not exactly a flip flop, does the same thing.
As a further step, you can build a system of sequential and combinatorial logic that can carry out operations depending on the bits stored in a memory system, including writing back new values to that memory system. Now you've arrived at the level of the processor, and everything the processor does, is just hardware carrying out lots of simple tasks. (microprogrammed cores notwithstanding). At this point, the particular combinations of bits that you put in the memory system can be considered machine language software.
Best Answer
OBL = Option Byte Loader. Found it in this datasheet. At page 19 is a short description of what it does.
Probably that switch is automatically triggered in standby/battery mode.
In Radiofrequency applications, IF usually means Intermediate Frequency. But in this case:
IF = Interface as PeterJ suggested in the first comment.