SRT512 datasheet(21/46 Pages) STMICROELECTRONICS

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SRT512

SRT512 states

Doc ID 13277 Rev 4

21/46

SRT512 states

The SRT512 can be switched into different states. Depending on the current state of the

SRT512, its logic will only answer to specific commands. These states are mainly used

during the anticollision sequence, to identify and to access the SRT512 in a very short time.

The SRT512 provides 6 different states, as described in the following paragraphs and in

Figure 18.

6.1

Power-off state

The SRT512 is in Power-off state when the electromagnetic field around the tag is not

strong enough. In this state, the SRT512 does not respond to any command.

6.2

Ready state

When the electromagnetic field is strong enough, the SRT512 enters the Ready state. After

Power-up, the Chip_ID is initialized with a random value. The whole logic is reset and

remains in this state until an Initiate() command is issued. Any other command will be

ignored by the SRT512.

6.3

Inventory state

The SRT512 switches from the Ready to the Inventory state after an Initiate() command has

been issued. In Inventory state, the SRT512 will respond to any anticollision commands:

Initiate(), Pcall16() and Slot_marker(), and then remain in the Inventory state. It will switch to

the Selected state after a Select(Chip_ID) command is issued, if the Chip_ID in the

command matches its own. If not, it will remain in Inventory state.

6.4

Selected state

In Selected state, the SRT512 is active and responds to all Read_block(), Write_block(), and

Get_UID() commands. When an SRT512 has entered the Selected state, it no longer

responds to anticollision commands. So that the reader can access another tag, the

SRT512 can be switched to the Deselected state by sending a Select(Chip_ID2) with a

Chip_ID that does not match its own, or it can be placed in Deactivated state by issuing a

Completion() command. Only one SRT512 can be in Selected state at a time.

6.5

Deselected state

Once the SRT512 is in Deselected state, only a Select(Chip_ID) command with a Chip_ID

matching its own can switch it back to Selected state. All other commands are ignored.

6.6

Deactivated state

When in this state, the SRT512 can only be turned off. All commands are ignored.

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