| type | bw | |
| read | 75μs | 1s/75μs*8k/1s=104m/s |
| write | 1300μs | 1s/1300μs*8k/1s=6m/s |
| erase | 3.8ms | 1s/3.8ms*8k*256/1s=526m/s |
| PCIe Gen2 x8 | 5Gbps | 5Gbps/8*8=4.88G/s |
| DDR3 | 533MHz（32bit） | 32bit*533MHZ/8=2.132GB/s |
|
system bus- AXI-Lite (bus width: 32 bits) |
Used for control Operates @ 100MHz |
|
|
storage data bus- AXI (bus width: 64 bits, burst length: 16) |
Used for DMA operations between flash storage controller/PCIe interface and DRAM Operates @ 100 MHz |
64bit*100MHZ/8=800m/s |
| flash bus | Operates @ 50MHz, DDR (100MB/s data rate) | 8bit*50MHZ/8=50m/s |
数据传输
PCIE <--DMA--AXI--> DRAM <--DMA--AXI> FSC <--flash bus--> DIE
FSC控制器结构如下：
Way arbiter
Way arbiter是用在当有多个way controller都要请求commonflash bus 和 access page buffer，因为是公用的，所以就要分配permission权限，算法如下：
lastGrantedWay = 0
while (true)
if (requestArrived)
for (i = 0 to numberOfWays)
nextCandidate = (lastGrantedWay + i) % numberOfWays //就是从上次使用的way继续往下轮训着找
if (hasRequested(nextCandidate))
grantPermission(nextCandidate)
permission权限的意思是指（每次只有一个way可以使用）：
● Access page buffer (through data path)
● Use flash bus
下面列出一个example：
Buffer controller
encoder/decoder
Buffer size is 2198B
● Data 2048B + 60B ECC parity + reserved (90B)
– Reserved space was intended to support more powerful ECC (currently not used)
● Page size of flash device is 8192B, thus, data transfer occurs 4 times
写过程：
读过程：
page结构
1.Physical page size of flash device
■ 8KB+448B (8640B)
2.There are four chunks
■ Each chunk consists of a pair of data and parity
3.Reserved 40B area is intended to store FTL metadata (currently not used)
way controller
下面来看flash controller的具体结构：
modules
②Page read, page program, block erase commands are executed in 2-3 stages