Primitive Component: Flash Wrapper
prim_flash is a wrapper interface for technology specific flash modules.
As the exact details of each technology can be different, this document mainly describes the interface requirements and their functions. The wrapper however does assume that all page sizes are the same (they cannot be different between data and info partitions, or different types of info partitions).
|NumBanks||int||Number of flash banks. Flash banks are assumed to be identical, asymmetric flash banks are not supported|
|InfosPerBank||int||Maximum number of info pages in the info partition. Since info partitions can have multiple types, this is max among all types.|
|InfoTypes||int||The number of info partition types, this number can be 1~N.|
|InfoTypesWidth||int||The number of bits needed to represent the info types.|
|PagesPerBank||int||The number of pages per bank for data partition.|
|WordsPerPage||int||The number of words per page per bank for both information and data partition.|
|DataWidth||int||The full data width of a flash word (inclusive of metadata)|
|MetaDataWidth||int||The metadata width of a flash word|
|TestModeWidth||int||The number of test modes for a bank of flash|
Overall Interface Signals
|flash_req_i||input||Inputs from flash protocol and physical controllers|
|flash_rsp_o||output||Outputs to flash protocol and physical controllers|
|prog_type_avail_o||output||Available program types in this flash wrapper: Currently there are only two types, program normal and program repair|
|init_busy_o||output||The flash wrapper is undergoing initialization|
|bist_enable_i||input||lc_ctrl_pkg :: On for bist_enable input|
|scanmode_i||input||dft scanmode input|
|scan_en_i||input||dft scan shift input|
|scan_rst_n_i||input||dft scanmode reset|
|flash_power_ready_h_i||input||flash power is ready (high voltage connection)|
|flash_power_down_h_i||input||flash wrapper is powering down (high voltage connection)|
|flash_test_mode_a_i||input||flash test mode values (analog connection)|
|flash_test_voltage_h_i||input||flash test mode voltage (high voltage connection)|
|flash_err_o||output||flash level error interrupt indication, cleared on write 1 to status register|
|flash_alert_po||output||flash positive detector alert|
|flash_alert_no||output||flash negative detector alert|
|flash_alert_ack||input||single pulse ack|
|flash_alert_trig||input||alert force trig by SW|
|tl_i||input||TL_UL interface for rd/wr registers access|
|tl_o||output||TL_UL interface for rd/wr registers access|
Flash Request/Response Signals
|prog_last||input||last program beat|
|prog_type||input||type of program requested: currently there are only two types, program normal and program repair|
|pg_erase||input||page erase request|
|bk_erase||output||bank erase request|
|erase_suspend||input||erase suspend request|
|addr||input||requested transaction address|
|part||input||requested transaction partition|
|info_sel||input||if requested transaction is information partition, the type of information partition accessed|
|he||input||high endurance enable for requested address|
|rd_data||output||transaction read data|
Theory of Operations
Transactions into the flash wrapper follow a req / ack / done format.
A request is issued by raising one of
bk_erase to 1.
When the flash wrapper accepts the transaction,
ack is returned.
When the transaction fully completes, a
done is returned as well.
Depending on the type of transaction, there may be a significant gap between
For example, a read may have only 1 or 2 cycles between transaction acknowledgement and transaction complete.
Whereas a program or erase may have a gap extending up to uS or even mS.
It is the flash wrapper decision on how many outstanding transaction to accept. The following are examples for read, program and erase transactions.
The flash wrapper may undergo technology specific intializations when it is first powered up.
During this state, it asserts the
init_busy to inform the outside world that it is not ready for transactions.
During this time, if a transaction is issued towards the flash wrapper, the transaction is not acknowledged until the initialization is complete.
Since flash programs can take a significant amount of time, certain flash wrappers employ methods to optimize the program operation.
This optimization may place an upper limit on how many flash words can be handled at a time.
The purpose of the
prog_last is thus to indicate when a program burst has completed.
Assume the flash wrapper can handle 16 words per program operation.
Assume a program burst has only 15 words to program and thus will not fill up the full program resolution.
On the 15th word, the
prog_last signal asserts and informs the flash wrapper that it should not expect a 16th word and should proceed to complete the program operation.
prog_type input informs the flash wrapper what type of program operation it should perform.
A program type not supported by the wrapper, indicated through
prog_type_avail shall never be issued to the flash wrapper.
Since erase operations can take a significant amount of time, sometimes it is necessary for software or other components to suspend the operation.
The suspend operation input request starts with
erase_suspend_req assertion. Flash wrapper circuit acks when wrapper starts suspend.
When the erase suspend completes, the flash wrapper circuitry also asserts
done for the ongoing erase transaction to ensure all hardware gracefully completes.
The following is an example diagram
flash_err_o is a level interrupt indication, that is asserted whenever an error event occurs in one of the Flash banks.
An Error status register is used to hold the error source of both banks, and it is cleared on writing 1 to the relevant bit.
Clearing the status register trigs deassertion of the interrupt.