HCS365_11 Datasheet, PDF(17/40 Page) Microchip Technology – KEELOQ® Code Hopping Encoder Crypt keys are read protected

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HCS365_11 Datasheet, PDF (17/40 Pages) Microchip Technology – KEELOQ® Code Hopping Encoder Crypt keys are read protected

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FIGURE 5-2: LED OPERATION

LED

VDD > VLOW

TLEDON

TLEDOFF

LED

VDD < VLOW

LEDBL=1

LED

VDD < VLOW

LEDBL=0

5.4 Cyclic Redundancy Check (CRC)

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 VLOW bit. The decoder can use

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: CRC Calculation

CRC[1]n + 1 = CRC[0]n â Din

and

CRC[0]n + 1 = (CRC[0]n â Din) â CRC[1]n

with

CRC[1, 0]0 = 0

and Din the nth transmission bit 0 <= n <= 64

5.5 Button Queue Information

(QUEUE)

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 002 and is incremented if a button is pushed

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.

HCS365

FIGURE 5-3:

CODE WORD COMPLETION

WITH QUEN SETTINGS

MTX = 012, WAKE > 002

QUEN = Disabled

DATA WAKE-UP CODE1

CODE1

WAKE-UP CODE2 CODE2

QUEN = Enabled

DATA

WAKE-UP CODE1 00

WAKE-UP CODE2 01 CODE2 01

6.0 PROGRAMMING

SPECIFICATIONS

Refer to the âHCS365 Programming Specificationsâ

document (DS41157) in Microchip Literature.

DS41109E-page 17

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