Specifications

Chapter 6: The VMEbus Interface
Page 81
Example #2 performs a byte (8-bit) write into the VMEbus A32 space. Here the
upper 16 bits of the VME address need to be stored in the appropriate registers.
1. Set the VME access bit in register 8104h.
2. Set register 8150h with the value corresponding to the 8 high-order address bits.
VMEbus Address bits 31-24 WA31-24
3. Determine the correct address modifier for A32 supervisory access.
4. Calculate the value and set register 8151h as follows:
VME WA23-22 BORD IACK AM5 AM4 AM2 AM1
Bits 7 & 6 VME address bits 23-22
Bit 5 BORD = 0
Bit 4 IACK = 0
Bits 3-0 Bit 3 (Address Modifier bit 5)
Bit 2 (Address Modifier bit 4)
Bit 1 (Address Modifier bit 2)
Bit 0 (Address Modifier bit 1)
5. Set register 8130h with the value corresponding to bits 21-16 of the VMEbus
address with the two low order bits of the register set to 0.
VMEbus Address bits 21-16 Res Res
6. Map the address.
7. Write the data.