2.1Examples of two-pair wiring (for RS-422 circuit)
(1)When connecting one computer and one PC
Cable connection and signal direction | 485PC | Application | |||
Signal name | Signal name | ||||
|
| ||||
SDA | R*1 |
| RDA | Reception data | |
SDB |
| R*1 | Reception data | ||
|
| RDB | |||
RDA | R*1 |
| SDA | Transmission data | |
RDB |
| R∗1 | Transmission data | ||
|
| SDB | |||
LINK SG |
| LINK SG | Signal ground | ||
Grounding |
| FG *2 | Frame ground | ||
| 24V *3 | Power supply terminal | |||
resistance of | DC24V | ||||
100 Ω or less | 24G *3 | Power supply terminal | |||
FX base unit | |||||
(2)Computer and PCs in 1 : n connection ( n has a maximum value of 16 ).
The terminal lagout shown is diagrammatic only. As for 485ADP, see chapter 1, and as for
Computer
SD
RD
485ADP | 485ADP | Computer link unit | ||||
of A series PCs | ||||||
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|
|
| |||
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| Station | Station | Station |
| |
R *1 | No. 0 | No. 1 | No. 15 |
| ||
| SDA | SDA | SDA | SDA | *1 | |
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|
| R | |
SD | SDB | SDB | SDB | SDB |
| |
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|
|
| ||
R | *1 | RDA | RDA | RDA |
| |
| RDA | *1 | ||||
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|
| R | |
RD | RDB | RDB | RDB | RDB |
| |
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|
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| LINK | LINK | LINK | SG |
| |
| SG | SG | SG |
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| ||||
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| *2 | *2 | *2 |
| |
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| FG | FG | FG |
| |
*1 R is the terminating resistance. Connect the terminating resistance (330 Ω) between terminals
SDA and SDB , and terminals RDA and RDB . For details see section 2.3.
*2 Connect terminal FG to earth terminal | of the PC main body grounded with resistance of 100 |
Ωor less. However, as for the computer link unit of the A series PC, see the manual of the computer link unit.
*3 The 24V DC power requirement can be taker from the service power supply of the PC.
