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User’s Guide 21020285 D
Chapter 2 Hardware Essentials
Board Addressing Page 2 - 5
Board
Addressing
The Board Address and Slave Address Modifier to which the RF3880 responds
on the VMEbus are set with jumpers on the board.
Choosing an
Address
Modifier
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.
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 non-privileged access:
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.
Choosing a
VMEbus
Address
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.
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.
AM5 AM4 AM3 AM2 AM1 AM0
101
Jumper
In = 0
Out = 1
01
VMEAddress Modifier Lines
Table 2: Choosing an Address Modifier
Hex
Code
Address Modifier
Function
543210
2D101101Short Supervisory Access
29 Short Non-Privileged Access
Table 3: VMEbus Address Modifiers for RF3880
A15 A14 A13 A12 A11 A10 A9 A8 A7 A6 A5 A4 A3 A2 A1 A0
Address lines decoded to identify the
RF3880 base address which is set via
jumpers on the board.
Address
lines
decoded
to select
one of
four
ports.
Table 4: Address Line Decoding