cx28500 Mindspeed Technologies, cx28500 Datasheet - Page 130

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

Table 6-41.
6.8.7
The Buffer Status Descriptor (BSD) contains information regarding the data buffer processing. If BSD updates are
allowed, the information is written over the Buffer Descriptor. The BSD includes the following bit fields:
•
•
•
•
The Receive Buffer Status Descriptor contains an Error Status (ERROR) bit field.
The design of BSD and BD in the same location allows CX28500 to self-service the buffers without Host
intervention. See the Self Servicing Mechanism chapter.
Tables 6-42
Table 6-42.
28500-DSH-002-C
28
27:26
25:18
17:15
14
13:0
31
30
Bit
Bit
Owner Indicator Bit (ONR)
End Of Message Indicator (EOM)
Last MD in the table (LAST)
Data Length (DLEN)
and
Field Name
Field Name
BLEN[13:0]
CHAN [7.0]
Receive Buffer Descriptor (2 of 2)
RxLAST
Transmit Buffer Status Descriptor (1 of 2)
EOBIEN
RSVD/
RSVD
RSVD
ONR
6-43
NP
NOTE:
Buffer Status Descriptor
list the transmit and receive buffer status descriptors and their descriptions.
While operating in ECC mode, if configured to update the Buffer Status Descriptor, the
CX28500 writes both the BSD and the data buffer pointer. This is required in order to
perform a 64-bit PCI write transaction.
Value
Value
—
0
1
0
0
0
0
1
0
1
0
1
End Of Buffer Interrupt Disabled. When the last data byte is put into this buffer, an EOB interrupt is
generated.
End Of Buffer Interrupt Enabled. When the last data byte is put into this buffer, an EOB interrupt is
generated.
Reserved.
When operating in normal mode (i.e., not Preserve Channel Mode as indicated by bit PCHMODE in
Global Configuration Descriptor) this field is Reserved. When operating in Preserve Channel Mode,
this field is used by CX28500 to transfer the least significant 8 bits of the channel number. The most
significant bits are transferred to the data pointer.
Reserved
This is not the last MD in this message descriptor table.
This is the last MD in this message descriptor table.
Buffer Length. Actual number of received data bytes might be less than this. This number indicates
how many will fit into the data buffer. If BLEN=0, the RDMA ignores this MD and skips to the next one.
HOST Owns Buffer. Channel is to remain in idle mode while polling this bit periodically (if NP = 0) until
Host relinquishes control to CX28500 by setting ONR = 1.
CX28500 Owns Buffer. Continue processing data buffer normally.
Poll Enabled. If ONR = 0, Host-owned, CX28500 polls the message descriptor periodically while in idle
mode until ONR = 1.
Poll Disabled. If ONR = 0, then enter suspend mode and wait for a Channel Activate or Jump Host
Service from Host.
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Description
Description
Memory Organization
115