28440 Parallax Inc, 28440 Datasheet - Page 6

• Manufacturer Part Number: 28440
• Description: RFID Modules & Development Tools RFID Read/Write Serial Module
• Manufacturer: Parallax Inc

Specifications of 28440

• Operating Current: 10 mA
• Operating Voltage: 5 V
• Product: RFID Readers
• Wireless Frequency: 125 KHz
• Dimensions: 3.25 in x 2.45 in
• Operating Temperature Range: - 40 C to + 85 C
• For Use With/related Products: EM4x50
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Error Checking
The RFID Read/Write Module responds to each command with a single-byte status/error code in
hexadecimal format followed by any returned data, if applicable. In most standard implementations, the
user will repeatedly call the desired function until the ERR_OK status byte is returned, indicating that the
function successfully completed with no errors.
For scenarios where more error checking is desired, the RFID Read/Write Module provides detailed error
code values:
Tag Details
The RFID Read/Write Module works exclusively with the EM Microelectronics-Marin SA EM4x50 1kbit
R/W transponder tags at 125kHz. A variety of different tag types and styles exist with the most popular
ones made available from Parallax.
The memory map and corresponding address locations for the EM4x50 tag are shown below. Each
address holds a 32-bit (4 byte) value.
The User Data Area can be optionally secured using a 32-bit password to allow only authorized read and
write operations. This password is stored in
RFID_SetPass command with knowledge of the current password. For security reasons, it cannot be read.
As such, if your tag is password-protected and you forget the tag’s password, you will be unable to
retrieve the contents of the User Data Area.
ADDR_Protect
scenarios, should not be changed by the user.
Copyright © Parallax Inc.
Address (decimal)
Value
0x01
0x02
0x03
0x04
0x05
0x06
0x07
3-31
32
33
0
1
2
and
ERR_OK
ERR_LIW
ERR_NAK
ERR_NAK_OLDPW
ERR_NAK_NEWPW
ERR_LIW_NEWPW
ERR_PARITY
ADDR_Control
Name
ADDR_Password
ADDR_Protect
ADDR_Control
User Data Area
ADDR_Serial
ADDR_DeviceID
Register
RFID Read/Write Module, Serial (#28440)
are modified directly by the RFID Read/Write Module and, in normal
No Errors
Could not find a Listen Window (LIW) from the tag
Received a No Acknowledge (NAK), possible communication error or
invalid command/data
Received a No Acknowledge (NAK) sending the current password during
the RFID SetPass command, possible incorrect password
Received a No Acknowledge (NAK) sending the new password during the
RFID SetPass command
Could not find a Listen Window (LIW) from the tag after setting the new
password during the RFID SetPass command
Parity error when reading data from the tag
ADDR_Password
Password (not readable)
Protection word
Control word
Non-volatile EEPROM storage area for user data (116 bytes)
Device serial number (unique, read-only)
Device identification (used to identify tag family, read-only)
and can be changed by the user via the
Description
Description
v1.0 6/29/2010 Page 6 of 10