Panasonic KX-FT21BX Service Manual page 93

After the power is turned on, the ASIC(CPU) initializes and checks each IC.
The ROM, SRAM, and Modem are checked.
If initialization fails for the ICs, the system will not boot up.
AC POWER ON
[1] Power check
+5 V: Is there +5 V at pin 7 of CN1?
+3.3 V: Is there +3.3 V at Q2 CORRECTOR?
[2] Oscillation
[3] Reset
Reset: IC1 (ASIC) 14 pin
A WDERR Constant 0V
B
A
4mS
[4] Check each signal line.
D0~D7
1
A0~A16
Use this 2
3 RD
order.
ROMCS
WR
RAMCS
X3=24MHz
OK
C Constant 5V
5V
0V
A WDERR
OK
See page 70.
NG
Problem with the power supply
unit.
NG
Check Q2, Q3 and Q1.
*Check IC1 (ASIC) 82 pin = 6MHz.
Constant 0V
B
Check the reset signal line
and reset IC (IC4).
Constant 5V
C
Check the status by test types
A, B, C and D. See page 68.
NG
See page 69.
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KX-FT21LA