Why Do We Need Flash In Bluetooth Module

Question

I understand that flash memory is used to store some program in microcontroller, it's erase programmable. But after look at HC-05 bluetooth module, there are 2 chips on the board. One chip is CSR bluetooth core-4 and one chip is for flash 2Mbit (seen on datasheet here!).

My Questions are:

1. What is flash usage here? is every bluetooth module had to have a flash chip? is it for writing and erasing data spread tranceived by bluetooth over and over?
2. On the datasheet it is stated that 2Mbit flash . From my prior knowledge bit usually bit referencing for speed not for storage (byte). or is it typo?

Answer 1

The external Flash is almost certainly storing the firmware for the CSR chip. A Bluetooth stack is not a small or simple piece of software. The use of off-die flash is probably for cost reasons, I believe it's difficult to integrate large amounts of flash with normal CMOS logic chips.

Answer 2

I can answer part 2): No that is not a typo.

Memory chips (DRAM, SRAM, flash, EEPROMS, etc etc.) are often sized in bits.
If you wish you can divide by eight to get the size in standard bytes.

(_{Usually by 8. Some systems like older mainframes use different byte sizes. E.g. 10 bits})