AUTOHELM Masterview ST80, Manual

Page: 15 / 22

At the same time, TR13 is cut off and stops TR11 conducting.
Battery B1 supplies RAM IC15 through diode D16, thus preserving the data
in the memory for the next power - up.
The reset signal (RESET) to the RAM is protected from spurious triggering
by integrator C31/R57 on the input to transistor TR10.
Checks on the charge state of battery B1 are made by signal B_SENSE
applied to transistor TR19, which generates signal B_LEVEL to ASIC IC4.
Autohelm ASIC
The ASIC is a custom-designed IC which provides specific facilities and
functions. These are:
1. Conversion of duplex SeaTalk data to Transmit and Receive format
(STDATA)
2. Beeper drive signals
3. Monitoring of VHELD, VUNREG and VCC, giving an orderly shutdown of
the software in the event of supply failure or intentional switch-off, via
signal PWR_FAIL
4. Watchdog timing (WDOG)
5. Reset. (RST)
Buzzer frequency and watchdog interval are set by R - C networks external
to the ASIC.
Z211Z211Z211Z211Z211
ST80 Masterview
ST80 Masterview Service Manual 83028-1 15