DOWNLOAD Panasonic KX-MB1900UCB / KX-MB2020UCB (serv.man2) Service Manual ↓ Size: 17.86 MB | Pages: 127 in PDF or view online for FREE

25

KX-MB1900UCB/KX-MB2020UCB

R23

PIO13

O

3.3V

NOT USED

R24

PIO12

O

3.3V

NOT USED

R25

PIO14

O

3.3V

NOT USED

R26

PIO15

I

3.3V

INPUT PORT

T01

SDMD0

I/O

3.3V

SDRAM DATA BUS 0

T02

SDMD1

I/O

3.3V

SDRAM DATA BUS 1

T03

NSDCAS

O

3.3V

SDRAM CAS

T04

NSDRAS

O

3.3V

SDRAM RAS

T11

VSS

-

GND

GND

T12

VSS

-

GND

GND

T13

VSS

-

GND

GND

T14

VSS

-

GND

GND

T15

VSS

-

GND

GND

T16

VSS

-

GND

GND

T23

PIO9

O

3.3V

OUTPUT PORT(SNPICK)

T24

PIO8

O

3.3V

NOT USED

T25

PIO10

O

3.3V

NOT USED

T26

PIO11

O

3.3V

OUTPUT PORT(SNREG)

U01

SDMD2

I/O

3.3V

SDRAM DATA BUS 2

U02

SDMD3

I/O

3.3V

SDRAM DATA BUS 3

U03

NSDWE

O

3.3V

SDRAM WRITE ENABLE

U04

VDD1.2

-

1.2V

POWER SUPPLY

U23

VDD3.3

-

3.3V

POWER SUPPLY

U24

PIO0

I

3.3V

INPUT PORT (HOOK)

U25

PIO1

O

3.3V

OUTPUT PORT(EXTRLY)

U26

PIO7

O

3.3V

NOT USED

V01

SDMD4

I/O

3.3V

SDRAM DATA BUS 4

V02

SDMD5

I/O

3.3V

SDRAM DATA BUS 5

V03

SDCKE

O

3.3V

SDRAM CLOCK ENABLE

V04

SDMA12

O

3.3V

SDRAM ADDRESS BUS 12

V23

PSCIO20

I

3.3V

INPUT PORT (CIS HOME)

V24

PSCIO21

O

3.3V

NOT USED

V25

PSCIO22

O

3.3V

NOT USED

V26

PSCIO23

O

3.3V

NOT USED

W01

SDMD6

I/O

3.3V

SDRAM DATA BUS 6

W02

SDMD7

I/O

3.3V

SDRAM DATA BUS 7

W03

SDMA11

O

3.3V

SDRAM ADDRESS BUS 11

W04

SDMA9

O

3.3V

SDRAM ADDRESS BUS 9

W23

PSCIO16

O

3.3V

NOT USED

W24

PSCIO17

I

3.3V

INPUT PORT (FANDET2)

W25

PSCIO18

I

3.3V

INPUT PORT (TOPCVR)

W26

PSCIO19

I

3.3V

INPUT PORT (PSTART)

Y01

VSS

-

GND

GND

Y02

SDCLK

O

3.3V

SDRAM CLOCK 1

Y03

SDMA8

O

3.3V

SDRAM ADDRESS BUS 8

Y04

VSS

-

GND

GND

Y23

AFESEL0

I

3.3V

NCU INTERFACE

Y24

AFESEL1

I

3.3V

NCU INTERFACE

Y25

EXMDMCS

O

3.3V

NOT USED

Y26

DP

O

3.3V

NCU INTERFACE

PIN NO.

PinName

I/O

POWER SUPPLY VOLTAGE

EXPLANATION

26

KX-MB1900UCB/KX-MB2020UCB

1. Function

This unit has a lithium battery (BAT300) which works for the Real Time Clock IC (RTC: inside IC300).
The RTC continues to work, backed up by a lithium battery even when the power switch is OFF.

2. RTC Inside (IC300) Backup Circuit Operation

When the power switch is turned ON, power is supplied to the RTC (inside IC300). At this time, the voltage at pin AF3 of the
IC300 is +3.3V. When the power switch is turned OFF, the BAT300 supplies power to RTC through DA300. 
When the power switch is OFF and the voltage of +3.3V decreases, pin AF3 of RTC (IC300) becomes roughly the same volt-
age as the battery voltage. RTC goes into the backup mode, in which the power consumption is lower.

27

KX-MB1900UCB/KX-MB2020UCB

The modem (Included IC300) has all the hardware satisfying the CCITT standards mentioned previously.
ALL processing is controlled by the SOC (IC300) according to CCITT procedures.
This modem (Included IC300) has an automatic application equalizer. With training signal 1 or 2 at the time of G3 reception, it can
automatically establish the optimum equalizer.  

The digital image data sent on ATXD line from modem (Included IC300) .
DAA IC100(6

→9,10), Line side DAA IC101 and the NCU section to the telephone line.

The analog image data which is received from the telephone line passes through the NCU section and enters line side DAA*

IC100. The signals are changed to digital data in IC101 (5,6) ,IC100(9,10

→5) and IC300. In this case, the image signals from

the telephone line are transmitted serially. Here, the internal equalizer circuit reduces the image signals to a long-distance
receiving level. This is designed to correct the characteristics of the frequency band centered around 3 kHz and maintain a con-
stant receiving sensitivity.

The path is the same as Facsimile Reception.

This is the call signal which is generated the SOC (IC300) and sent to the speaker.

 DAA : Direct Access Arrangement

28

KX-MB1900UCB/KX-MB2020UCB

Composed of ITS circuit and NCU circuit.

The analog section works as an interface between the telephone line.
DAA control ITS circuit and NCU circuit. 
DAA control signals are output from Soc IC300.

[NCU]: Network Control Unit the NCU comprises of the following; DC loop forming circuit to connect with the telephone line;
Switching circuit for other interconnected telephones; Bell detection circuit; Remote fax activation circuit.
Refer to NCU Section (KX-MB2020 ONLY) (P.29) for the details.

RING

ARXD

ATXD

BTXD

BRXD

IC200

IC100

IC101

EXTRLY

T

R

T

R

SP(+)

SP(-)

HS_MIC(+)

HS_MIC(+)

HS_SP(+)
HS_SP(-)

15

5

6

5

6

10

9

8

9

15

1

16

14

12

1

3

13

4

5

10

16

KX-MB2020UCB: MAIN BOARD BLOCK DIAGRAM