HCS473 Datasheet, PDF (35/68 Pages) Microchip Technology – Code Hopping Encoder and Transponder

HCS473
FIGURE 3-22:
Calculating Communication TE
SKIPACK = 0 - Field Acknowledge sent when device wakes
125 kHz Field
(on LC pins)
Simultaneous LF
Acknowledge
(LFRSP=1)
TSF
TCMD
Command
Inductive
(LC)
RF
Response
(DATA)
8LFTE
3LFTE 3LFTE 3LFTE
8LFTE
RF Acknowledge
(RFRSP=1)
Communication from reader to HCS473
Communication from HCS473 to reader
TCMD
3.2.8
RFEN DURING LF
COMMUNICATION (Figure 3-23)
3.2.8.1 Wake-up Sequence
The wake-up Acknowledge sequence has the shortest,
but fixed, PLL setup time, 1LFTE.
3.2.8.2 Transponder Select Sequence
PLL setup occurs on the rising edge of the first VID bit
in anticipation of the TID Acknowledge. The setup time
before the ACK begins is therefore a function of...
• LF baud rate
• VID value
• TID value
3.2.8.3
ACK Response Sequences
Concluding with CRC
Command sequences ending with CRC bits and
expecting an Acknowledge response have a similar
PLL setup sequence. This includes “Present Transport
Code”, “Write” and “Anticollision Off”.
PLL setup occurs on the rising edge of the first CRC bit
in anticipation of the Acknowledge. The setup time is
therefore a function of...
• LF baud rate
• CRC value
• Response time: TTPACK, TWRT, TAOACK.
3.2.8.4
Data Response Sequences
Concluding with CRC
Command sequences ending with CRC bits and
expecting data response (code hopping word) have a
similar PLL setup sequence. This includes “IFF”,
“Read” and “Request Hopping Code”.
PLL setup occurs on the rising edge of the first CRC bit
in anticipation of the data transmission. The setup time
is therefore a function of...
• LF baud rate
• CRC value
• Response time: TIFF, TREAD, THOP.
 2002 Microchip Technology Inc.
Preliminary
DS40035C-page 33