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21020285 D User’s Guide
Appendix E Design Differences
Page E - 4 Implementation Differences
Implementation
Differences
The following descriptions explain changes made to the way the RF3880
implements features:
Width of Data Transfers on the VMEbus
Because the RF3880 implements new bus specifications for VME D64, there
have been changes to the way that the VMEbus width is selected.
The width of any data transfer now depends on the Address Modifier supplied,
and the value of the WID Bit in the Control Field of the Address Buffer Port.
The WID bit is shown in Table 6 on page 2 - 8. When WID is 0, 16-bit transfers
are forced. When WID is 1, 32 or 64 bit transfers will be used, dependent on
the Address Modifier used. Address Modifiers 08H, 0CH, 38H, and 3CH will
cause 64 bit transfers.
Note that the width of data transfers also depends naturally on the actual data
transfer address. Complete 16, 32, or 64 bit transfers can only occur when the
address has the proper alignment (to word, longword, or double-longword).
The RF3880 will perform smaller width transfers until the proper address
alignment is reached. The adapter will then shift into the maximum width
allowed by the WID bit and the Address Modifier.
Status Port Error Codes and Test Flags
The RF3880 has a new, high performance hardware architecture. This new
hardware requires different Status Port Error Codes. These are shown in Table
10 on page 2 - 13. Status Port Error Codes 14H, 1CH, and codes C0H to CCH
are no longer used. Codes 80H, 84H, 88H, 8CH, and D0H were added.
Additionally, in the Diagnostic Command’s Test Flag field, Bit 3 is now the
RAM test bit. See Table 79 on page 7 - 24.
Extended SCSI ID’s
The SCSI-3 specification, in addition to allowing 16-bit data transfers, supports
16 SCSI ID’s. (Previous products were limited to eight.) Changes were made
in the following areas to accommodate the additional SCSI ID’s:
SCSI Configuration Jumper Block - A hardware jumper for the extra bit
(SCSI ID Bit 3) of the SCSI ID was necessary. Changes were made to the SCSI
Configuration Jumper Block in order to implement this. The new arrangement
of the jumper block is shown in Table 13 on page 3 - 6.
The Board Information Command reports the jumper setting of the SCSI
Configuration Jumper Block, in the SCSI Cfig Block byte. Since the jumpers
were rearranged, the value expected in this byte might change. See Table 98
on page 7 - 37.
Identify and Board Information Commands - Both of these commands
return an Option Flags field that now uses Bit 0 to report SCSI ID Bit 3. For
Identify command see Table 64 on page 7 - 10. For the Board Information
command, see Table 92 on page 7 - 34.
Additionally, the Board Information Command Parameter Block has a new
field, shown on Table 91 on page 7 - 33. Called the Options field, its purpose
is to allow you choose whether information for all possible SCSI ID’s is
returned or information is limited to eight.