HCS473 Datasheet, PDF (24/68 Pages) Microchip Technology – Code Hopping Encoder and Transponder

HCS473
3.2.2.4 Command Sequence
The transponder reader follows the HCS473’s Field
Acknowledge by sending the desired 3-bit command,
3-bit option or address, associated data and CRC;
each as required. LF commands are Pulse Position
Modulated (PPM) as shown in Figure 3-10. The last bit
(CRC bit) should be followed by leaving the field on for
TFINH.
TFINH should be appropriately adjusted to receive con-
secutive commands or LF responses. See
Section 3.2.4 and Section 3.2.5 for LF response and
consecutive command considerations.
FIGURE 3-11:
HCS473 TRANSPONDER WAKE-UP SEQUENCE
SKIPACK = 0 - Field Acknowledge sent when device wakes
125kHz Field
(on LC pins)
Simultaneous LF
Acknowledge
(LFRSP=1)
TSF
TCMD
Command
Inductive
(LC)
RF
Response
(DATA)
3LFTE 3LFTE 3LFTE
RF Acknowledge
(RFRSP=1)
TCMD
SKIPACK = 1 - Field Acknowledge is not sent
TSF_MAX
Inductive
(LC)
Communication from reader to HCS473
Communication from HCS473 to reader
Command
TCMD
DS40035C-page 22
Preliminary
 2002 Microchip Technology Inc.