Chapter 2 Hardware Essentials
Board Addressing | Page 2 - 5 |
Board
Addressing
Choosing an
Address
Modifier
The Board Address and Slave Address Modifier to which the RF3880 responds on the VMEbus are set with jumpers on the board.
The RF3880 adapter is an A16 SLAVE device on the VMEbus. In keeping with VMEbus specifications, the Address Modifier for selection of this type of device can be either 29H or 2DH. Since there is only one bit difference between the two values, a single jumper is provided to select an Address Modifier.
AM5 | AM4 | AM3 | AM2 | AM1 | AM0 |
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1 | 0 | 1 | In = 0 | 0 | 1 |
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VMEAddress Modifier Lines
Table 2: Choosing an Address Modifier
Choose Address Modifier 2DH by removing the jumper, when you wish to reserve the RF3880 registers for short supervisory access. Choose 29H by inserting the jumper, if you wish to allow short
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Code | 5 | 4 |
| 3 | 2 |
| 1 | 0 | |
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2D | 1 | 0 |
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| 0 | 1 | Short Supervisory Access |
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29 |
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Table 3: VMEbus Address Modifiers for RF3880
Choosing a
VMEbus
Address
The factory setting for the RF3880 Slave Address Modifier is 2DH; the jumper is out.
The location and setting of this jumper is described in Chapter 3, Hardware Installation.
With the address jumpers on the RF3880 board, you set the upper 7 bits of the Board Address. This effectively reserves 512 bytes of VMEbus 16- bit address space. Within the reserved area, the RF3880 adapter has four register ports that are the foundation of its communication scheme.
A15 | A14 | A13 | A12 | A11 |
| A10 | A9 | A8 | A7 | A6 | A5 | A4 | A3 | A2 | A1 | A0 |
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Address lines decoded to identify the |
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RF3880 base address which is set via |
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Table 4: Address Line Decoding
The factory setting, for the RF3880 VMEbus Address, is to jumper A12, making the default base address EE00H. Details about the location and setting of the jumpers can be found in Chapter 3, Hardware Installation.
User’s Guide | 21020285 D |
