UM0290 datasheet(48/76 Pages) STMICROELECTRONICS

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Mass storage demo

UM0290

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5.3.6

SCSI protocol implementation

The aim of the SCSI Protocol is to provide a correct response to all SCSI commands

needed by the operating system on the PC host. This section details the method of

management for all implemented SCSI commands.

●

INQUIRY Command (OpCode = 0x12):

Send the needed inquiry page data (in this demo only the page 0 and the standard

page are supported) with the needed data length according to the ALLOCATION

LENGTH field of the command.

●

SCSI READ FORMAT CAPACITIES Command (OpCode = 0x23):

Send the Read Format Capacities data response (ReadFormatCapacity_Data[ ]

from the files SCSI_data.c).

●

SCSI READ CAPACITY (10) Command (OpCode = 0x25):

Send the Read Capacity (10) data response (ReadCapacity10_Data[ ] from the

file SCSI_data.c).

●

SCSI MODE SENSE (6) Command (OpCode = 0x1A):

Send the Mode Sense (6) data response (Mode_Sense6_data[

]

from the file

SCSI_data.c).

●

SCSI MODE SENSE (10) Command (OpCode = 0x5A):

Send the Mode Sense (10) data response (Mode_Sense10_data[ ] from the file

SCSI_data.c).

●

SCSI REQUEST SENSE Command (OpCode = 0x03):

Send the Request Sense data response. Note that the Request_Sense_Data [ ]

array (file SCSI_data.c) is updated using the function Set_Scsi_Sense_Data() in

order to set the Sense key and the ASC fields according to any error occurring during

the transfer.

●

SCSI TEST UNIT READY Command (OpCode = 0x00):

Always return a CSW with COMMAND PASSED status.

●

SCSI PREVENT\ALLOW MEDIUM REMOVAL Command (OpCode = 0x1E):

Always return a CSW with COMMAND PASSED status.

●

SCSI START STOP UNIT Command (OpCode = 0x1B):

This command is sent by the PC host when a user right-clicks on the device (in

Windows) and selects the Eject operation. In this case the firmware programs the data

in the internal Flash using the function Stor_Data_In_Flash().

●

SCSI READ10 (OpCode = 0x28) and SCSI WRITE 10 (OpCode = 0x2A):

The host issues these two commands to perform a read or a write operation. In these

cases the device has to verify the address compatibility with the memory range and the

direction bit in the bmFlag of the command. If the command is correctly validated the

firmware launches the read or write operation from the internal RAM.

●

SCSI VERIFY 10 (OpCode =0x2F):

The Verify command requests the device to verify the data written on the medium. In

this case no Flash-like memory support is used, so when the command Verify is

received, the device tests the BLKVFY bit. If set to one, a Command Passed status is

returned in the CSW.

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