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

{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

{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

{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

{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.