HCS370_11 Datasheet, PDF (6/42 Pages) Microchip Technology – KEELOQ® Code Hopping Encoder Four selectable baud rates

HCS370
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 2-2(D)
VDD
P
DATA, RFEN
STEP
Outputs
N
Figure 2-2(E)
VIN
-
+
1.2V
FIGURE 2-3: I/O CIRCUITS (CONTINUED)
Figure 2-3(A)
S0, S1, S2
S3, S4, SHIFT
Inputs
ZIN
Figure 2-3(B)
S5/SLEEP
ZIN
N
VDD
P
N
S5
SLEEP
SOEN
Figure 2-3(C)
LED Output
VDD
Weak P
LED
N
LED
DS41111E-page 6
2011 Microchip Technology Inc.