hcs365 Microchip Technology Inc., hcs365 Datasheet - Page 17

• Manufacturer Part Number: hcs365
• Description: Keeloq Code Hopping Encoder
• Manufacturer: Microchip Technology Inc.

FIGURE 5-2:
5.4
The CRC bits are calculated on the 65 previously trans-
mitted bits. These bits contain the 32-bit hopping code,
32-bit fixed code, and V
the CRC bits to check the data integrity before process-
ing starts. The CRC can detect all single bit errors and
66% of double bit errors. The CRC is computed as fol-
lows:
EQUATION 5-1:
and
with
and Di
5.5
The queuing or repeated pressing of the same buttons
can be handled in two ways on the HCS365. This is
controlled with the Queue Counter Enable (QUEN)
configuration option. This option can be different for
Encoder 1 and Encoder 2.
When the QUEN option is disabled, the device will reg-
ister up to two sequential button presses. In this case,
the device will complete the minimum code words
selected with the MTX option before the second code
word is calculated and transmitted. The code word will
be 67 bits in this case, with no additional queue bits
transmitted.
If the QUEN option is enabled, the queue bits are
added to the standard code word. The queue bits are a
2-bit counter that does not wrap. The counter value
starts at 00
within 2 seconds from the start of the previous button
press. The current code word is terminated when a but-
ton is queued. This allows additional functionality for
double or triple button presses.
SN
LED
V
LED
V
LEDBL=1
LED
V
LEDBL=0
2002 Microchip Technology Inc.
DD
DD
DD
> V
< V
< V
CRC 0
n
the nth transmission bit 0
Cyclic Redundancy Check (CRC)
Button Queue Information
(QUEUE)
LOW
LOW
LOW
2
and is incremented if a button is pushed
CRC 1
n
T
+
LEDON
1
LED OPERATION
=
CRC 1 0
n
+
CRC Calculation
CRC 0
1
LOW
T
=
LEDOFF
CRC 0
bit. The decoder can use
0
n
=
<=
Di
0
n
n
n
<=
64
Di
CRC 1
n
n
Preliminary
FIGURE 5-3:
6.0
Refer to the “HCS365 Programming Specifications”
document (DS41157) in Microchip Literature.
DATA
DATA
QUEN = Enabled
QUEN = Disabled
SN
WAKE-UP
WAKE-UP
PROGRAMMING
SPECIFICATIONS
CODE1
CODE1
CODE WORD COMPLETION
WITH QUEN SETTINGS
00
CODE1
WAKE-UP
WAKE-UP
HCS365
CODE2 01
DS41109D-page 17
MTX = 01
CODE2
2
, WAKE > 00
CODE2 01
CODE2
2