Brother P-touch PT-2310, Service Manual

Page: 73 / 113

III-7
Powering-on sequence (See Fig. 3.2-7.)
1) Interrupted by IRQO, the CPU starts the chattering elimination program module.
2) If pin 38 is Low for 10 ms, the CPU recognizes the “On/Off ( )” key as being pressed
and then transfers the control to the main program module. If pin 38 is High, the CPU
interprets the input as a noise and waits for the next IRQO.
Fig. 3.2-7 Powering-on and -off Sequence
3) Even if releasing the “On/Off ( )” key makes a chattering noise so as to generate
IRQO, the CPU interprets the signal as a noise for 10 ms (between A and B) and then
transfers the control to the main program module.
Powering-off sequence (See Fig. 3.2-7.)
1) Interrupted by IRQO, the CPU starts the chattering elimination program module.
2) If pin 38 is Low for 10 ms, the CPU recognizes the “On/Off ( )” key as being pressed
and then transfers the control to the sleep program module. If pin 38 is High, the CPU
interprets the input as a noise and keeps the main program module.
3) Even if releasing the “On/Off ( )” key makes a chattering noise so as to generate
IRQO, the CPU interprets the signal as a noise for 10 ms (between C and D) and then
transfers the control to the sleep program module.
[ 2 ] Power saving circuit
The circuit diagram of the power saving circuit is shown in Fig. 3.2-6. If you power off the machine
with the power “On/Off (
)” key or you make no key entry for approx. 5 minutes (for approx. 30
minutes when the machine uses the USB interface), the CPU turns P0W High to cut off the Vcc
(which normally would feed power to the logic circuits except the CPU). This way, the CPU enters
the sleep mode where oscillation stops so as to feed no clock to the CPU.
In the stand-by mode, the 3.3BV feeds power only to the CPU.
To cancel the power saving mode (automatic powering-off mode) and resume the normal
operation mode, press the power “On/Off (
)” key.