cx28500 Mindspeed Technologies, cx28500 Datasheet - Page 90

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

Table 6-5.
6.2.1.2
Each SRD is 4 dwords. The SRDs used by CX28500 are as follows:
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•
•
28500-DSH-002-C
CH_DEACT
EBUS_WR
OPCODE
EBUS_RD
Device Configuration Descriptor (DCD)
EBUS Configuration Descriptor (ECD)
Channel Configuration Descriptor (CCD)
CH_JMP
CH_ACT
RSVD
Service Request Descriptor—OPCODE Description (2 of 2)
8h-1Fh
Value
Service Request Descriptors
3h
4h
5h
6h
7h
Channel Activation.
This is a request to activate a single channel. CX28500 assumes that the channel was already configured. If the
channel is currently active, this command results in a destructive termination of the current message being
processed, as well as flushing any other messages residing in the channel’s FIFO. CX28500 fetches the channel’s
new head pointer from shared memory (actually from the Transmit Head Pointer Table (THPT) or Receive Head
Pointer Table (RHPT)), before it internally activates the channel. The Service Request Descriptor used for this
command is Channel Configuration Descriptor.
Channel Deactivation.
This is a request to deactivate a channel. This command results in a destructive termination of the current message
being processed, and flushing of any other messages residing in the channel’s FIFO. The SRD used for this
command is Channel Configuration Descriptor.
Channel Jump.
This is a request to jump to a new head pointer buffer descriptor. If there is an active transfer of a message from or
to shared memory, the channel jump service request command (CH_JMP) is not executed until an EOM indication is
received. When an EOM indication is received (or if there is no active transfer), CX28500 fetches a new head pointer
buffer descriptor for this channel from shared memory (actually from the Transmit Head Pointer Table (THPT) or
Receive Head Pointer Table (RHPT)).
EBUS Write.
This is a request to execute write transaction(s) over the EBUS. Data is copied from Host memory to the EBUS.
EBUS Read.
This is a request to execute read transaction(s) over the EBUS. Data is copied from the EBUS Address specified in
the 3rd dword of EBUS Configuration Descriptor to the shared memory location specified in the 2nd dword of EBUS
Configuration Descriptor. The data length copied from one location to another location is specified by LENGTH bit
field in EBUS Configuration Descriptor. Note: The EBUS_RD and EBUS_WR Service Request mechanism allow a
maximum of 16 K dwords transfer to/from the EBUS. The transaction is split to bursts of 32 dwords over the PCI.
Reserved
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Mindspeed Technologies
Description
®
Memory Organization
75