User Manual

2.6 The RS-485 Port & Self-Tuner ASIC

The 2-wire RS-485 port is designed to directly drive 7000 series modules.

It is a half-duplex 2-wire RS-485 network. Send/receive directional control in a

2-wire RS-485 network is very important. Therefore, the 7521 series equip a

Self-Tuner ASIC controller for all RS-485 ports. The Self-Tuner ASIC

controller will auto detect & control the send/receive direction of the RS-485

network. In this main, the application program does not have to be worried

about the send/receive direction control of the RS-485 network. For example,

the software program for one-to-one communication is nearly the same.

ToCom(port, sent_data); /* send one sent_char to RS-232/RS-485 */

no direction control */

while IsCom(port); /* wait one echo_char from RS-232/RS-485 */

echo_data=ReadCom(port); /* read this echo_data */

7521 series

Inside

Self-Tuner ASIC

RS-485  Data+, Data-

RS-232  TXD, RXD, GND

Send/receive direction

Auto detect/control

2-wire RS-485 network

7521/2/2A/3/4/7 Series Hardware User’s Manual, Ver. 1.5 Sep/2002, 7Mh-001-15 -----53