DOWNLOAD Panasonic KX-NCP1172XJ Service Manual ↓ Size: 2.07 MB | Pages: 47 in PDF or view online for FREE

9

• EC bus interface

Independent bus for 16bit/8MHz two-way address data multiplex.

• CT bus interface

Supports eight 8.192MHz highways (128 time slots).

• Local bus interface

HITACHI-manufactured (Data 8bit, Address 13bit) SH-1CPU-compatible bus.

• Local highway interface

Accommodates 2.048, 4.096, and 8.192MHz highways (Up to 64 time slots).

• Local TSW

Exchanges the time slots between CT bus (1024ch) and local highway (64ch).

• Local gain control

Controls the gain of the local highway up-and-down 64ch in 1db step arbitrarily.

• PT interface

Allows APT/DPT interface to be selected for each port.

• GPIO interface

Parallel interface that is arbitrarily programmable bidirectionally.

• Time slot structure

The following is the time slot structure of the local highway on NCP1172.

10

• DPT data communications

Bch/Dch/Cch data is transmitted from the DTL/DTH terminal of ASIC, and the AMI-converted pulse signal is output to DPT
(between D1 and D2) by way of the driver U5 and the pulse transformer T1. The Bch/Dch/Cch data transmitted from APT is input
to the DR terminal of ASIC by way of the pulse transformer T1 and R13. ASIC compares VREF+ and VREF- with the input wave-
form, and receives a valid pulse.

• Bch communications

Communicated by the PCM data (64kbps x 2) connected from the local highway by ASIC.
Used mainly for the audio signal of DPT.

• Dch communications

Communicated by the data (16kbps) protocol-converted by the HDLC controller in ASIC.
Used mainly for the control signal of DPT.

• Cch communications

Communicated by the data (8kbps) converted by the serial/parallel-converting circuit in ASIC.
Used mainly for recognizing the terminal model.

11

• PT current-supply circuit

+15V/+40V is superimposed on the transmit/receive data line (D1, D2), and fed to PT. Supply voltage is +15V for old DPT and
APT, and +40V for new DPT. It will be switched after the connected PT is judged through communications. I/O control is as
follows.

For the protection against such as an over current owing to +15V short in wiring, 300mA constant-current circuit by Q1, Q2, and
R25 is used. In case of +40V, 20mA and 80mA constant-current circuits by Q4, U3, R7, and R27 are used.
The following is the flow chart of telephone switching at boot-up.

PT_POW

PT_CUR

H

H

15V

H

L

0V

L

H

40V80mA

L

L

40V20mA

12

This circuit generates +3.3V, +5V from the input +15V.
It is comprised of the circuit that steps +15V down to +3.3V by the switching power supply of IC801, Q801, and L810 and the
one that steps +15V down to +5V by the switching power supply of IC802, Q802, and L811.
It has two protection circuits : IP1 against +3.3V short and +5V short, and the over voltage protection that detects the voltage
build up of +3.3V/+5V, turns Q16 on, and then stop supplies of +15V.