HCS361 datasheet(7/42 Pages) MICROCHIP

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DS40146F-page 7

HCS361

3.5

CONFIG

(Configuration Word)

The Configuration 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 configurations. Further

explanations of each of the bits are described in the

following sections.

TABLE 3-1:

CONFIGURATION WORD

3.5.1

MOD: MODULATION FORMAT

MOD selects between VPWM modulation and PWM

modulation format.

If MOD = 1, VPWM modulation is selected as well as

the following:

Enables the TXWAK bit to select the WAKE-UP

transmission.

Extends the Guard Time.

If MOD = 0, PWM modulation is selected.

3.5.2

BSEL: BAUD RATE SELECT

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

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

833 bits per second.

3.5.3

TXWAK: BIT FORMAT SELECT OR

WAKE-UP

In PWM mode, this bit selects the bit format.

If TXWAK = 0, the PWM pulse duty cycle is 1/3-2/3.

If TXWAK = 1, the PWM pulse duty cycle is 1/6-2/6.

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

If TXWAK = 0, transmissions start normally with the

preamble portion of the code word.

If TXWAK = 1, transmissions start with a Wake-up

sequence followed by a dead time (see Figure 4-2).

The following tables summarize the combined effect of

TXWAK, BSEL and MOD option bits.

TABLE 3-1:

PWM OPTIONS

TABLE 3-2:

VPWM OPTIONS

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).

3.5.5

OVR: OVERFLOW

The overflow bit is used to extend the number of possi-

ble synchronization values. The synchronization coun-

ter is 16 bits in length, yielding 65,536 values before the

cycle repeats. Under typical use of 10 operations a day,

this will provide nearly 18 years of use before a

repeated value will be used. Should the system

designer conclude that is not adequate, then the over-

flow bit can be utilized to extend the number of unique

values. This can be done by programming OVR to 1 at

the time of production. The encoder will automatically

clear OVR the first time that the transmitted synchroni-

zation value wraps from 0xFFFF to 0x0000. Once

cleared, OVR cannot be set again, thereby creating a

permanent record of the counter overflow. This pre-

vents fast cycling of 64K counter. If the decoder system

is programmed to track the overflow bits, then the effec-

tive number of unique synchronization values can be

extended to 128K. If programmed to zero, the system

will be compatible with old encoder devices.

Bit Number Symbol

Bit Description

0BACW

Blank Alternate Code Word

BSEL

Baud Rate Selection

TXWAK

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

2/3 select

VPWM mode: Wake-up

enable

SPM

Sync Pulse Modulation

SEED

Seed Transmission enable

5DELM

Delay mode enable

6TIMO

Time-out enable

7IND

Independent mode enable

USRA0

User bit

USRA1

User bit

USRB0

User bit

USRB1

User bit

XSER

Extended serial number

enable

TMPSD

Temporary seed

transmission enable

MOD

Modulation format select

OVR

Overflow bit

Note:

The Wake-up sequence is transmitted

before the first code word of each trans-

mission only.

MOD TXWAK

BSEL

Duty Cycle

400us

1/3-2/3

200us

1/3-2/3

200us

1/6-2/6

100us

1/6-2/6

MOD TXWAK

BSEL

Wake-up

400us

200us

400us

YES

200us

YES

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