| # Primitive Component: Flash Wrapper |
| |
| # Overview |
| `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). |
| |
| ## Parameters |
| |
| Name | type | Description |
| ---------------|--------|---------------------------------------------------------- |
| 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 |
| |
| |
| ## Signal Interfaces |
| |
| ### Overall Interface Signals |
| Name | In/Out | Description |
| ------------------------|--------|--------------------------------- |
| clk_i | input | Clock input |
| rst_ni | input | Reset input |
| 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 |
| tck_i | input | jtag tck |
| tdi_i | input | jtag tdi |
| tms_i | input | jtag tms |
| tdo_o | output | jtag tdo |
| 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_ni | 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 |
| |
| Name | In/Out | Description |
| -------------------|--------|--------------------------------- |
| rd | input | read request |
| prog | input | program request |
| 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 |
| prog_data | input | program data |
| ack | output | transaction acknowledge |
| rd_data | output | transaction read data |
| done | output | transaction done |
| |
| |
| |
| # Theory of Operations |
| |
| ## Transactions |
| |
| Transactions into the flash wrapper follow a req / ack / done format. |
| A request is issued by raising one of `rd`, `prog`, `pg_erase` or `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 `ack` and `done`. |
| 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. |
| |
| ### Read |
| ```wavejson |
| {signal: [ |
| {name: 'clk_i', wave: 'p.................'}, |
| {name: 'rd_i', wave: '011..0.1..0.......'}, |
| {name: 'addr_i', wave: 'x22..x.2..x.......'}, |
| {name: 'ack_o', wave: '010.10...10.......'}, |
| {name: 'done_o', wave: '0....10...10....10'}, |
| {name: 'rd_data_o', wave: 'x....2x...2x....2x'}, |
| ]} |
| ``` |
| |
| ### Program |
| ```wavejson |
| {signal: [ |
| {name: 'clk_i', wave: 'p................'}, |
| {name: 'prog_i', wave: '011...0.1....0...'}, |
| {name: 'prog_type_i', wave: 'x22...x.2....x...'}, |
| {name: 'prog_data_i', wave: 'x22...x.2....x...'}, |
| {name: 'prog_last_i', wave: '0.......1....0...'}, |
| {name: 'ack_o', wave: '010..10.....10...'}, |
| {name: 'done_o', wave: '0..............10'}, |
| ]} |
| ``` |
| |
| ### Erase |
| ```wavejson |
| {signal: [ |
| {name: 'clk_i', wave: 'p................'}, |
| {name: '*_erase_i', wave: '01.0.........1.0.'}, |
| {name: 'ack_o', wave: '0.10..........10.'}, |
| {name: 'done_o', wave: '0.....10.........'}, |
| ]} |
| ``` |
| |
| ## Initialization |
| |
| The flash wrapper may undergo technology specific initializations 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. |
| |
| ## Program Beats |
| |
| 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. |
| |
| ## Program Type |
| The `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. |
| |
| ## Erase Suspend |
| 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 |
| ```wavejson |
| {signal: [ |
| {name: 'clk_i', wave: 'p................'}, |
| {name: 'pg_erase_i', wave: '01.0..............'}, |
| {name: 'ack_o', wave: '0.10...10........'}, |
| {name: 'erase_suspend_i', wave: '0.....1.0........'}, |
| {name: 'done_o', wave: '0............10..'}, |
| ] |
| } |
| ``` |
| |
| ## Error Interrupt |
| The `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. |
