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HCS412 数据表(PDF) 22 Page - Microchip Technology |
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HCS412 数据表(HTML) 22 Page - Microchip Technology |
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22 / 52 page  HCS412 DS41099D-page 22 © 2011 Microchip Technology Inc. 4.3.2 READ The transponder reader sends one of seven possible read commands indicating which 16-bit EEPROM word to retrieve (Table 4-4). The HCS412 retrieves the data and returns the 16-bit response. Each Read response is preceded by a 1LFTE low START pulse and ‘01b’ preamble (Figure 4-4). The following locations are available to read: • The 64-bit general purpose user EEPROM. (USER[3:0]). • The 32-bit serial number (SER[1:0]). The serial number is also transmitted in each code hopping transmission. • The16-bit Configuration word containing all non- security related options. FIGURE 4-4: READ 4.3.3 WRITE The transponder reader sends one of seven possible write commands (Table 4-5) indicating which 16-bit EEPROM word to write to. The 16-bit data to be written follows the command. The HCS412 will attempt to write the value into EEPROM and respond with an Acknowl- edge sequence if successful. The following locations are available to write: • The 64-bit general purpose user EEPROM. (USER[3:0]) (Figure 4-6). • The 32-bit serial number (SER[1:0]). The serial number is also transmitted in each code hopping transmission (Figure 4-5). • The16-bit Configuration word containing all non- security related configuration options. If the con- figuration is written, the device must be RESET before the new settings take effect (Figure 4-5). A Transport Code, write access password, protects the serial number and configuration word from undesired modification. For these locations the reader must follow the WRITE command with the appropriate 28-bit trans- port code, then the 16 bits of data to write. Only a cor- rect match with the transport code programmed during production will allow write access to the serial number and configuration word (Figure 4-5). The delay to a successful write Acknowledge will vary depending on the number of bits changed. TABLE 4-4: LIST OF READ COMMANDS Command Description Expected data In Response 00001 Read Configuration word None 16-bit Configuration word 00010 Read low serial number None Lower 16 bits of serial number (SER0) 00011 Read high serial number None Higher 16 bits of serial number (SER1) 00100 Read user EEPROM 0 None 16 Bits of User EEPROM USR0 00101 Read user EEPROM 1 None 16 Bits of User EEPROM USR1 00110 Read user EEPROM 2 None 16 Bits of User EEPROM USR2 00111 Read user EEPROM 3 None 16 Bits of User EEPROM USR3 16-bit Start TRT 01 2 LFTE 01b Preamble Command Response Communication from reader to HCS412 Communication from HCS412 to reader ACK Start 1 LFTE TPU TATO Activate Field ACK Delay to Command Command Delay until Response 16-bit Response 6 LFTE |
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