Data Sheet
Copyright © Parallax Inc.  RFID Read/Write Module, Serial & USB (#28440 / 28540) v2.1 2/27/2018 Page 6 of 10 
0x05: RFID_Protect 
Enable (lock) or disable (unlock) the tag’s password protection.  
Input: Mode (1 byte), 0x00 to unlock, 0x01 to lock 
Output: Status byte (1 byte) 
Example:  
SEROUT RFID_TX, Baud, ["!RW", RFID_Protect, 1]  ' Lock the tag 
SERIN RFID_RX, Baud, [err]       ' Get status byte 
Note: When the tag is locked, a successful login using the RFID_Login command is required before you 
can enable/disable password protection, change the tag’s password, or read/write to the tag. If the tag is 
locked and you are not successfully logged in, the RFID_Read command will return four bytes of 0x00 in 
place of the actual user data and the RFID_Write command will return an error. 
0x06: RFID_Reset 
Log out and reset the tag.  
Input: None 
Output: Status byte (1 byte) 
Example:  
SEROUT RFID_TX, Baud, ["!RW", RFID_Reset]   ' Reset the tag 
SERIN RFID_RX, Baud, [err]       ' Get status byte 
Note: All user data will remain stored on the tag. You will need to re-login using RFID_Login if you want 
to access a locked tag after calling this command. You can also reset the tag by removing it from the 
proximity of the RFID Read/Write Module.  
0x0F: RFID_ReadLegacy 
Read the 40-bit unique serial number from an EM Microelectronics EM4100 read-only tag (used with 
Parallax’s RFID Card Reader Serial, #28140, and USB, #28340).  
Input: None 
Output: Header (1 byte) + data (10 bytes) + footer (1 byte) 
Example: 
SEROUT RFID_TX, Baud, ["!RW", RFID_ReadLegacy]   ' Read EM4100 unique serial # 
SERIN RFID_RX, Baud, [header, STR data\10, footer]  ' Get header, data, and footer 
Note: The header and footer are used to identify that a correct string has been received from the reader 
(they correspond to a line feed and carriage return characters, respectively). The middle ten bytes are 
the tag's unique ID sent in a printable ASCII string. For example, for a tag with a valid ID of 0F0184F07A, 
the following bytes would be sent: 0x0A, 0x30, 0x46, 0x30, 0x31, 0x38, 0x34, 0x46, 0x30, 0x37, 0x41, 
0x0D.  










