HCS360 Datasheet, PDF (7/24 Pages) Microchip Technology – KEELOQ CODE HOPPING ENCODER

HCS360
3.5.3 SEED: ENABLE SEED TRANSMISSION
If SEED = 0, seed transmission is disabled. The inde-
pendent counter mode can only be used with seed
transmission disabled since SEED_2 is shared with the
second synchronization counter.
With SEED = 1, seed transmission is enabled. The
appropriate button code(s) must be activated to trans-
mit the seed information. In this mode, the seed infor-
FIGURE 3-1: SEED TRANSMISSION
All examples shown with XSER = 1, SEED = 1
When S[3:0] = 1001, delay is not acceptable.
CRC+VLOW SER_1
SEED_2
For S[3:0] = 0x3 before delay:
mation (SEED_0, SEED_1, and SEED_2) and the
upper 12- or 16-bits of the serial number (SER_1) are
transmitted instead of the hop code.
Seed transmission is available for function codes
(Table 3-7) S[3:0] = 1001 and S[3:0] = 0011(delayed).
This takes place regardless of the setting of the IND bit.
The two seed transmissions are shown in Figure 3-1.
SEED_1
SEED_0
Data transmission direction
16-bit Data Word
16-bit Counter
Encrypt
CRC+VLOW SER_1
SER_0
Encrypted Data
Data transmission direction
For S[3:0] = 0011 after delay (Note 1, Note 2):
CRC+VLOW SER_1
SEED_2
SEED_1
SEED_0
Data transmission direction
Note 1: For Seed Transmission, SEED_2 is transmitted instead of SER_0.
2: For Seed Transmission, the setting of DELM has no effect.
© 1996 Microchip Technology Inc.
Preliminary
DS40152C-page 7