HCS370ST datasheet(6/36 Pages) MICROCHIP

6 / 36 page

HCS370

DS41111D-page 6

Preliminary

2002 Microchip Technology Inc.

If the device is in the transmit process and detects that

a new button is pressed, the current code word will be

aborted, a new code word will be transmitted and the

time-out counter will RESET. If all the buttons are

released, a minimum number of code words will still be

completed. The minimum code words can be set to 1,

2, 4, or 8 using the Minimum Code Words (MTX) con-

figuration option. If the time for transmitting the mini-

mum code words is longer than the time-out time, the

device will not complete the minimum code words.

The HCS370 has an onboard nonvolatile EEPROM.

This EEPROM is used to store user programmable

data and the synchronization counter. The data is pro-

grammed at the time of production and includes the

security related information such as encoder keys,

serial numbers, discrimination values, and seed val-

ues. All the security related options are read protected.

The initial counter value is also programmed at the time

of production. From then on the device maintains the

counter itself. The HCS370 has built in redundancy for

counter protection and can recover from counter cor-

ruption.

The counter will not increment if the previous write was

corrupted by low voltage RESET or power failure dur-

ing TPLL. Instead, the counter will revert back to the

previous count and the HCS370 will attempt to correct

the bad bits. This will continue on every button press

until the voltage increases and the counter is success-

fully corrected.

FIGURE 2-2:

I/O CIRCUITS

FIGURE 2-3:

I/O CIRCUITS (

CONTINUED)

DATA, RFEN

Figure 2-2(D)

STEP

Outputs

VIN

Figure 2-2(E)

1.2V

VDD

S0, S1, S2

Inputs

S3, S4, SHIFT

ZIN

Figure 2-3(A)

LED Output

LED

Figure 2-3(C)

VDD

LED

Weak

S5/SLEEP

ZIN

VDD

SOEN

Figure 2-3(B)

SLEEP

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