Chapter 8 host bus interface (hbi), 1 functional overview, 2 host memory mapping – SMSC LAN9311i User Manual
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Two Port 10/100 Managed Ethernet Switch with 16-Bit Non-PCI CPU Interface
Datasheet
SMSC LAN9311/LAN9311i
99
Revision 1.4 (08-19-08)
DATASHEET
Chapter 8 Host Bus Interface (HBI)
8.1
Functional Overview
The Host Bus Interface (HBI) module provides a high-speed asynchronous SRAM-like slave interface
that facilitates communication between the LAN9311/LAN9311i and a host system. The HBI allows
access to the System CSRs and handles byte swapping based on the dynamic endianess select. The
HBI interfaces to the switch fabric via the Host MAC, which contains the TX/RX Data and Status FIFOs,
Host MAC registers and power management features. Refer to
Chapter 9, "Host MAC," on page 113
for detailed information on the Host MAC.
The following is an overview of the functions provided by the HBI:
Asynchronous 16-bit Host Bus Interface:
The HBI provides an asynchronous SRAM-like Host Bus
Interface that is compatible with most CPUs.
Host data bus endianess control:
The HBI supports dynamic selection of big and little endian
host byte ordering based on the END_SEL input pin. This highly flexible interface provides mixed
endian access for registers and memory.
Direct FIFO access modes:
When the FIFO_SEL input pin is high during host access, all host
write operations are to the TX data FIFO and all host read operations are from the RX data FIFOs.
This feature facilitates operation with host DMA controllers that do not support FIFO operations.
System CSR’s:
The HBI allows for configuration and monitoring of the various LAN9311/LAN9311i
functions through the System Control and Status Registers (CSRs). These registers are accessible to
the host via the Host Bus Interface and allow direct (and indirect) access to all the LAN9311/LAN9311i
functions. For a full list of all System CSR’s and their descriptions, refer to
Interrupt support:
The HBI supports a variety of interrupt sources. Individual interrupts can be
monitored and enabled/disabled via registers within the System CSRs for output on the IRQ pin. For
more information on interrupts, refer to
Chapter 5, "System Interrupts," on page 49
For a list of all HBI related pins, refer to
Chapter 3, Pin Description and
.
8.2
Host Memory Mapping
The host memory map has two unique modes: normal operation mode, and direct FIFO access mode.
During normal operation, the base address decode map is as described in
allowing access to the full range of System Management CSRs and the TX/RX Data and Status FIFOs.
This is the default mode of operation. The second mode of operation is the direct FIFO access mode.
In direct FIFO access mode, all host write operations are to the TX Data FIFO and all host read
operations are from the RX Data FIFO. Refer to
Section 14.1.3, "Direct FIFO Access Mode," on
for additional information.
8.3
Host Data Bus
The host data bus is 16-bits wide. Two writes or reads must be performed back-to-back, as detailed
below, for proper communication.
Note:
When accessing the device, the pair of cycles must be atomic. The first host bus cycle is
performed to the low/high WORD and the second host bus cycle is performed to the high/low
WORD forming a 32-bit transaction with no cycles to the LAN9311/LAN9311i in between. With
the exception of A[1], all address and control signals must be the same for both 16-bit cycles
of a 32-bit transaction.