Panasonic KX-FT21RS Serivce Manual page 101

6.3.2. ASIC (IC1)
This custom IC is used for general FAX operations.
1. CPU
This model uses a Z80 equivalent CPU operating at 6MHz.
Many of the peripheral functions are handled by custom designed LSIS. As a result, the CPU only needs to process the result.
2. RTC
Real time clock.
3. DECODER
Decodes the address.
4. MODEM
Execute modulation and demodulation for the FAX.
5. ROM/RAM I/F
Controls the SELECT signal of ROM or RAM and bank switching.
6. CIS I/F
Controls document reading.
7. IMAGE DATA RAM
This is inside the ASIC and has 8KB which is used for image processing.
8. THERMAL HEAD I/F
Transmits the recorded data to the thermal head.
9. MOTOR I/F
Controls the motor which feeds the document and feeds the reading document.
10. OPERATION PANEL I/F
Serial interface with Operation Panel.
11. I/O PORT
I/O Port Interface (for analog board port control).
12. ANALOG UNIT
Electronic volume for the handset and monitor.
Sends beep tones, etc.
Explanation of the Pin Distribution (IC1)
Pin Pin Name Buffer Power supply
1 X32OUT
2 X32IN
3 VDDRTC
4 XBACKEN
5 VDDSRAM
6 XRAMCS
7 XRAMCE2/ALARM
8 FTG
9 F1
10 MULT3/5
11 VSS
12 F2/OP50
13 FR/OP51
14 XRESET
15 VSS
16 XORESET
17 XRESETI
18 XWDERR
19 XRSTSWO/OP82
20 VIDRST/IOP20
21 SPHCLK/IOP21
22 DARKON/IOP22
23 ADSEL2/IOP23
24 BELL/OP
25 3.3V
5V Tolerant
VDDRTC -
VDDRTC NO
VDDRTC YES
VDDSRAM -
VDDSRAM -
MULT3/5 NO
MULT3/5 NO
MULT3/5 NO
MULT3/5 NO
3.3V YES
3.3V -
3.3V YES
3.3V YES
3.3V YES
3.3V YES
3.3V YES
3.3V YES
3.3V YES
3.3V YES
Signal Name I/O
X32OUT 32.768kHz oscillator for RTC (built-in feed back
resistor)
X32IN 32.768kHz oscillator for RTC (built-in feed back
resistor)
+3.3V/BATT 32.768kHz backup power supply for RTC
XRESET Backup enable
+3.3V/BATT RAMCS buffer/backup power supply for reset
VDDSRAM SRAM chip select ("H": 3.3V or BATT)
OPEN Not used
FTG O FTG
F1 O F1 (50%/75% selector)
+5V Power supply
DG Ground
E O LCD control
OPEN O Not used
XRESET Reset input for internal digital circuit
DG Ground
XORESET Reset output
XRESETI Voltage detector IC output for reset
XWDERR Watch dog timer error
OPEN O Not used
OPEN O Not used
OPEN O Not used
OPEN O Not used
OPEN O Not used
OPEN O Not used
+3.3V Power supply
101
KX-FT21RS
Description