cx28500 Mindspeed Technologies, cx28500 Datasheet - Page 131

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

Table 6-42.
Table 6-43.
28500-DSH-002-C
29
28
27:26
25:18
17:15
14
13:0
31
30
29
28
27:26
Bit
Bit
Field Name
Field Name
PADCNT[7:0]
BLEN[13:0]
RSVD [7:0]
EOBIEN
RSVD
EOM
Transmit Buffer Status Descriptor (2 of 2)
Receive Buffer Status Descriptor
ONR
EOBIEN
TxLAST
IC[1:0]
ABORT
NP
EOM
Value
0
1
0
1
0
Value
1-7
—
—
0
1
0
1
0
1
2
3
0
0
1
CX28500 Owns Buffer. Until CX28500 relinquishes control, the data in this descriptor is being used by
CX28500.
Host Owns Buffer. CX28500 has relinquished control of buffer back to Host. CX28500 is done processing
buffer.
No Poll. Copied from Receive Buffer Descriptor.
End Of Message Indicator. The last byte for this message is not in this buffer.
End Of Message indicator. The last byte for this data message is in this buffer either because a valid
closing flag (7Eh) was detected or the receiver terminated due to an error condition.
EOB Interrupt Enabled. Copied from Receive Buffer Descriptor.
Reserved
End Of Message Indicator clear–this is not the last buffer for the current message.
End Of Message Indicator set –this is the last buffer for the current message.
End Of Buffer Interrupt Disabled. When the last data byte is taken from this buffer, an EOB interrupt is
not generated.
End Of Buffer Interrupt Enabled. When the last data byte is taken from this buffer, an EOB interrupt is
generated.
Idle Code Select—If the protocol is HDLC, the Idle Code Select is 7Eh. If the protocol selection is
transparent, the Idle Code Select is FFh.
Idle Code Select—If the protocol is HDLC, the Idle Code Select is FFh. If the protocol selection is
transparent, the Idle Code Select is 7Eh.
Idle Code Select—00h.
Reserved.
Pad Count/Reserved.
When operating in normal mode (i.e., not in Preserve Channel Mode) this field is treated as
PADCOUNT. PADCNT indicates the minimum number of idle codes to be inserted between the closing
flags and the next opening flag (7Eh). If PADCNT = 2 and IC = 1, for example, CX28500 outputs the bit
pattern 7Eh..FFh..FFh..7Eh. There is no indication by CX28500 if more than PADCNT number of idle
codes are inserted. When operating in Preserve Channel Mode, this field is treated as a reserved field
whose bits are preserved in the Transmit Buffer Status Descriptor.
Packet should be transmitted and end correctly.
Packet transmission should end with ABORT sequence.
This is NOT the last MD in this message descriptor table.
This is the last MD in this message descriptor table.
Buffer Length. The number of bytes in data buffer to be transmitted. In general, this would equal the
allocated buffer size. If EOM = 1 and BLEN = 0, CX28500 is requested to generate HDLC abort
sequence. If EOM = 0 and BLEN = 0, the DMA ignores this BD and skips to the next one.
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Description
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Memory Organization
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