Sony PCS-1500, Service Manual

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3-37
PCS-1500/1500P
3-2-6. Overall Function of IF-745 Board
[System outline]
The IF-745 board is the communication interface board that establishes the communication interface
between the compact processor (PCS-P150/P150P) and terminal adapter (TA) that has the V.35
interface. The IF-745 board is installed as an optional interface of the MA-97 board. The number of
connection ports of the IF-745 board is one. When establishing connection with the IF-745 board
without using call control, only the V.35 interface is used. If you want automatic dialing and recep-
tion using call control, connect the IF-745 board using the V.35 interface and the RS-366 interface.
The IF-745 board consists of the transceiver block, receive call detection block, host interface block
and voltage converter block.
The functions of the respective circuit blocks are described below.
1. Transceiver block
The characteristics of both the transmitting and receiving signal, are converted between the balanced
transmission signal (conforming to the V.35 electrical characteristics) and the digital TTL level by the
V.35 transceiver (IC101). The signal transmission is performed in the form of a balanced signal in
which the signal amplitude must swing both in the positive and negative directions. It requires
±
5V
power supply voltage for the V.35 transceiver (IC101). On the other hand, all of the call control
signals are unbalanced transmission signals (conforming to the V.28 electrical characteristics) that can
be directly interfaced with the EIA-232C electrical characteristics. Therefore, conversion between the
V.28 electrical characteristics and the TTL level is performed using the EIA-232C transceivers
(IC200, IC201, IC202, and IC203).
2. Receive call detection and memory check blocks
When either RI that is the V.35 interface control signal or DLO that is the RS-366 interface control
signal goes active, these circuit blocks (IC204, IC205 and IC206) activates the receive call interrupt
signal to notify the TDM ASIC of the MA-97 board and also the host interface of the reception of
data.
3. Host interface block
The PLD (IC105) has the control function over the host interface, and an address decoder function
and four I/O ports.
4. Voltage converter block
Because the power supply voltage that is introduced to this board is only the single
+
5 V DC,
_
5 V
power is generated using the charge-pump type voltage converter (IC100).
The block diagram of the IF-745 board is shown in Fig. 3-22.
3-2. Circuit Description of the Respective Boards