cx28500 Mindspeed Technologies, cx28500 Datasheet - Page 66

• Manufacturer Part Number: cx28500
• Description: Cx28500 Multichannel Synchronous Communications Controller
• Manufacturer: Mindspeed Technologies

4.0 Expansion Bus (EBUS)
CX28500 provides access to a local bus interface on the CX28500 called the Expansion Bus (EBUS), which
provides a Host processor to access any address in the peripheral memory space on the EBUS.
Although EBUS utilization is optional, the most notable applications for the EBUS are the connections to peripheral
devices (e.g., Bt8370/Bt8398 T1/E1 framers, CX28398 (Octal DS1/E1 framers), CX28314/CX28313 (multiplexer-
demultiplexer DS1 to DS3 plus framer) that are local to CX28500’s serial port.
Unlike other generations of Conexant’s HDLC controllers (CX28478/CX28474A/CX28472A/CX28471A), CX28500
provides access to the EBUS through an interface similar to a mailbox interface. This interface provides all the
EBUS read and write accesses to be carried over the PCI bus, allowing PCI bursts. This mechanism improves the
PCI utilization when multiple EBUS accesses are necessary for accessing the configuration of the peripheral
devices. The PCI Function 1 is disabled. Therefore, CX28500’s EBUS service requests are capable of accepting or
generating burst on the PCI bus. However, the EBUS interface signals are not capable of performing burst.
Figures 4-1
and
4-2
illustrate block diagrams of the EBUS interface with and without local microprocessor (MPU).
Figure 4-1.
EBUS Functional Block Diagram with Local MPU
Local
EBUS
Expansion
Bus
Interface
Regenerated
and
Clock
Clock
Inverted
MPU
Address/Data
Address/Data
Control
T1/E1
or T3/E3
Bus Arbitration
Bus
Framers
Arbiter
500052_017
®
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28500-DSH-002-C
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