Introduction:
NOR type flash memory is a type of non-volatile memory that is commonly used in various electronic devices such as computers, smartphones, and digital cameras. It allows for high-speed data storage and retrieval, making it suitable for applications that require frequent read and write operations.

Data Erasure in NOR Type Flash Memory:
In NOR type flash memory, data is erased blockwise. This means that instead of erasing individual bits or bytes, the memory erases entire blocks of data at a time. This block-based erasure process is one of the key characteristics of NOR flash memory and distinguishes it from other types of memory technologies.

Block Erasure Process:
The block erasure process in NOR flash memory involves the following steps:

1. Selecting the Block: The first step is to select the block that needs to be erased. Each block typically consists of multiple pages, which are further divided into sectors. The memory controller identifies the specific block that needs to be erased based on the address provided by the system.

2. Erasing the Block: Once the block is selected, the erase operation is performed on the entire block. The erasure process involves applying a high voltage to the memory cells within the block, which causes the stored charge to be removed. This effectively resets the state of all the memory cells in the block to an erased state.

3. Verification: After the erasure process is completed, the memory controller performs a verification step to ensure that the block has been successfully erased. This involves reading the data from the erased block and comparing it to the expected erased state. If any errors are detected, the erase operation may be repeated or flagged as unsuccessful.

4. Status Update: Once the block is successfully erased and verified, the memory controller updates the status information to indicate that the block is now available for programming or writing new data.

Advantages of Blockwise Erasure:
The blockwise erasure process in NOR flash memory offers several advantages:

- Efficiency: Erasing data at the block level is more efficient compared to erasing at the bit or byte level. It reduces the number of erase cycles required, leading to faster overall performance and improved longevity of the memory.

- Data Integrity: The blockwise erasure process helps maintain data integrity by ensuring that all the data within a block is either fully erased or fully retained. This reduces the chances of partial erasure or corruption during the erasure process.

- Parallelism: The blockwise erasure process allows for parallelism, where multiple blocks can be erased simultaneously. This improves the overall erase performance of the memory, making it suitable for applications that require high-speed data operations.

Conclusion:
In NOR type flash memory, data is erased blockwise. This block-based erasure process offers several advantages in terms of efficiency, data integrity, and parallelism. It allows for faster erase operations, improves the longevity of the memory, and ensures the integrity of the stored data.