HCS412P datasheet(10/44 Pages) MICROCHIP

10 / 44 page

HCS412

DS41099C-page 10

Preliminary

FIGURE 3-2:

CODE WORD ORGANIZATION

3.2.1

QUEUE COUNTER (QUE)

The QUE counter can be used to request secondary

decoder functions using only a single transmitter but-

ton. Typically a decoder must keep track of incoming

transmissions to determine when a double button press

occurs, perhaps an unlock all doors request. The QUE

counter removes this burden from the decoder by

counting multiple button presses.

The 2-bit QUE counter is incremented each time an

active button input is released for at least the

Debounce Time (TDBR), then reactivated (button

pressed again) within the Queue Time (TQUE). The

counter increments up from 0 to a maximum of 3,

returning to 0 only after a different button activation or

after button activations spaced greater than the Queue

Time (TQUE) apart.

The current transmission aborts, after completing the

minimum number of code words (Section 3.4.1), when

the active button input is released. A button re-activa-

tion within Queue Time (TQUE) then initiates a new

transmission (new synchronization counter, encrypted

data) using the updated QUE value.

Figure 3-3 shows the timing diagram to increment the

queue counter value.

FIGURE 3-3:

QUE COUNTER TIMING DIAGRAM

VLOW

1-Bit

Fixed Code Portion (37 Bits)

QUE

2 Bits

CRC

2 Bits

VLOW

1-Bit

SER 1

Most Sig 16 Bits

SER 0

Least Sig 16 Bits

BUT

4 Bits

Counter

Overflow

2 Bits

DISCRIM

10 Bits

Synchronization

16 Bits

Counter

S0 LC0 OVR1

OVR0

Hopping Code Portion Message (32 Bits)

Q1 Q0 C1 C0

MSb

LSb

69 Data bits

Transmitted LSb first.

32-bit Serial Number (XSER = 1)

Fixed Code Portion (37 Bits)

QUE

2 Bits

CRC

2 Bits

BUT

4 Bits

S0 LC0

SER 0

Least Sig16 Bits

BUT

4 Bits

Counter

Overflow

2 Bits

DISCRIM

10 Bits

Synchronization

16 Bits

Counter

S0 LC0 OVR1

OVR0

Hopping Code Portion Message (32 Bits)

Q1 Q0 C1 C0

MSb

LSb

69 Data bits

Transmitted LSb first.

SER 1

12 MSb’s

28-bit Serial Number (XSER = 0)

Shaded data included in CRC calculation

Input

Code Words

Transmitted

1st Button Press

All Buttons Released

2nd Button Press

QUE1:0 = 002

Synch CNT = X

QUE1:0 = 012

Synch CNT = X+1

t2 = 0

t1 > TDBP

t1 = 0

TDBR < t < TQUE

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