RE46C180S16F Datasheet, PDF (36/58 Pages) Microchip Technology – CMOS Programmable Ionization Smoke Detector ASIC with Interconnect, Timer Mode and Alarm Memory

RE46C180
4.9 User Lock Bit Programming
Test mode TM19 allows users to program the user
EE lock bit. Once the user EE lock bit is set, the pro-
grammed user EE data can not be changed unless the
lock bit is reset.
To enter this mode, follow these steps:
1. Power up with the bias condition shown in
Figure 4-1 to enter M0. At power-up:
TEST = IO = FEED = T2 = V_SS,
DETECT = V_DD.
2. Drive T2 input from V_SS to V_DD and hold at V_DD
to enter TM0.
3. Drive TEST from V_SS to V_DD and hold at V_DD.
4. Apply 19 clock pulses to the T2 input (V_DD to
V_SS and then back to V_DD) to enter in TM19
mode.
5. Hold TEST at V_DD and pulse IO once to set the
lock bit and store into the EEPROM memory.
6. To reset the lock bit from Step 5, drive TEST to
V_SS and pulse IO once.
TEST
VDD
VSS
VDD
T2
VSS
Min TSETUP1 = 10 µs
VDD
IO
VSS
MODE
M0
TM0 TM1
To set user EE lock bit
Min TPW1 = 10 µs
Min T1 = 20 µs
TM2 TM3 TM4 TM5 TM6
Min PW2 = 10 ms
TM18
TM19
To reset user EE lock bit
TEST
VDD
VSS
VDD
T2
VSS
Min TSETUP1 = 10 µs
Min TPW1 = 10 µs
Min T1 = 20 µs
VDD
IO
VSS
MODE
M0
FIGURE 4-9:
TM0 TM1 TM2 TM3 TM4 TM5 TM6
TM18
Timing Diagram for User Lock Bit Programming in Mode TM19
Min PW2 = 10 ms
TM19
DS22275A-page 36
 2011 Microchip Technology Inc.