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User’s Guide 21020285 D
Chapter 2 Hardware Essentials
Address Buffer Port Page 2 - 9
Control Field
Use this byte-wide field to tailor the RF3880 adapter’s use of the system bus.
With it, you can set-up the adapter to:
• Transfer data in 16-bit, 32-bit or 64-bit mode on the VMEbus.
• Byte or word swap command structures to be compatible with the byte
and word ordering of either Intel or Motorola architectures.
Byte and word swapping are further discussed in Chapter 8, Details of Usage.
The bit meanings of the Control Field are as follows:
Note
For any of the control
bits to be considered
valid by the adapter, the
SET bit must be one.
BSC Byte Swapping Control - Defines whether high and low bytes of a
word will be swapped during transfer of status and parameter blocks.
0 ⇒ No swapping.
1 ⇒ Change byte order.
WSC Word Swapping Control - Defines whether high and low words of a
double word will be swapped during transfer of status and parameter blocks.
0 ⇒ No swapping.
1 ⇒ Change word order.
WID WIDth of data transfers - Determines (in conjunction with VMEbus
Address Modifier) the width of data transfers across the system bus.
Note
The RF3880 supports
64-bit wide block
transfers for only those
Address Modifiers listed
in the VME
specification.
0 ⇒16-bit data transfers.
(forces 16-bit transfers regardless of Address Modifier used.)
1 ⇒32-bit or 64-bit data transfers, dependent on the Address Modifier used.
SET select new control SETtings - Determines whether the rest of the bits
in the Control Field should be applied to adapter operation.
0 ⇒ ignore all other bits.
1 ⇒ apply bit values to next transfer.
76543210
SET 0 0 0 0 WID WSC BSC
Table 7: Control Field of Address Buffer Port