
9
STP2002QFP
Fast Ethernet, Parallel Port, SCSI (FEPS) - STP2002QFP
Sun Microsystems,
SBUS ADAPTER 22.1 Introduction
The SBus Adapter (SBA) is the layer between the Channel Engine Interface
(CEI) and the SBus. It provides one master port on the SBus side to funnel
three DMA channel engines (CE) onto the SBus, and one slave port for SBus
accesses to the CEs. The SBA can be viewed as a block of data path and flow
control between SBus and channel engine interface.
2.2 SBus Capabilities
2.2.1 Slave Accesses
• Supports byte/half-word/word access, but not burst transfer
• Supports 32-bit transfer mode
• Parity generation/checking
• Does not generate late error
• Does not generate Rerun Ack
• Maximum latency < 22 SBus clocks
2.2.2 Master Accesses
• Compliant to IEEE 1496
• Supports 64-bit/32-bit transfer mode
• Supports byte/half-word/word transfer size
• Supports burst transfer size from 8 bytes to 64 bytes
• Parity generation/checking
• Does not issue atomic transaction
• Does not support bus sizing
2.2.3 Address Decoding
In order to eliminate the need of NEXUS driver in between FEPS device driv-
er and the kernel there are no registers insides the SBA block (a register inside
SBA would be a global register which means a NEXUS driver is needed).
However, SBA does decode the physical address input and the access size for