HCS361 Datasheet, PDF(6/24 Page) Microchip Technology

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HCS361 Datasheet, PDF (6/24 Pages) Microchip Technology – KEELOQ CODE HOPPING ENCODER

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HCS361

3.2 SYNC_A, SYNC_B

(Synchronization Counter)

This is the 16-bit synchronization value that is used to

create the hopping code for transmission. This value

will be changed after every transmission. A second syn-

chronization value can be used to stay synchronized

with a second receiver.

3.3 SEED_0, SEED_1, and SEED_2

(Seed Word)

This is the three word (48 bits) seed code that will be

transmitted when seed transmission is selected. This

allows the system designer to implement the secure

learn feature or use this ï¬xed code word as part of a dif-

ferent key generation/tracking process or purely as a

ï¬xed code transmission.

3.4 SER_0, SER_1 (Encoder Serial

Number)

SER_0 and SER_1 are the lower and upper words of

the device serial number, respectively. There are 32 bits

allocated for the serial number and a selectable conï¬g-

uration bit determines whether 32 or 28 bits will be

transmitted. The serial number is meant to be unique

for every transmitter.

3.5 CONFIG (Conï¬guration Word)

The conï¬guration word is a 16-bit word stored in

EEPROM array that is used by the device to store

information used during the encryption process, as well

as the status of option conï¬gurations. Further

explanations of each of the bits are described in the

following sections.

TABLE 3-2 CONFIGURATION WORD

Bit Number

Symbol

BACW

FAST

TXWAK

SPM

SEED

DELM

TIMO

IND

USRA0

USRA1

USRB0

USRB1

XSER

TMPSD

VPWM

OVR

Bit Description

Blank Alternate Code Word

Baud Rate Selection

PWM mode: 1/6, 2/6 or 1/3,

2/3 select

VPWM mode: Wakeup

enable

Sync Pulse Modulation

Seed Transmission enable

Delay mode enable

Time out enable

Independent mode enable

User bit

Extended serial number

enable

Temporary seed transmis-

sion enable

VPWM select

Overï¬ow bit

3.5.1 BACW: BLANK ALTERNATE CODE WORD

BACW = 1 selects the encoder to transmit every sec-

ond code word. This can be used to reduce the average

power transmitted over a 100ms window and thereby

transmit a higher peak power.

3.5.2 FAST: SELECT FAST TRANSMISSION

FAST selects the baud rate. If FAST = 1, the baud rate

is nominally 1667 bits per second and with FAST = 0,

833 bits per second.

3.5.3 TXWAK: BIT FORMAT SELECT OR

WAKEUP

In PWM mode, this bit selects the bit format. If TXWAK

= 1, the PWM pulse is 1/6;2/6 and for TXWAK = 0, 1/

3;2/3 (Figure 4-1, VPWM = 0).

In VPWM mode, this bit enables the wake-up signal.

With TXWAK = 1, transmission of the wake-up and

dead time sequence is enabled (Figure 4-2, VPWM =

1). Wakeup is transmitted before the ï¬rst code word of

each transmission only. For TXWAK = 0, the transmis-

sion will skip wake-up and start transmitting the pream-

ble portion of the code word (Figure 4-2, VPWM = 1).

3.5.4 SPM: SYNC PULSE MODULATION

Select modulation mode of Sync Pulse. If SPM = 1, the

sync pulse is modulated (Figure 4-1 and Figure 4-2).

DS40146C-page 6

Preliminary

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