cx28500 Mindspeed Technologies, cx28500 Datasheet - Page 132

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

Table 6-43.
6.8.8
The Data Buffer Pointer, defined in
memory.
Table 6-44.
While operating in Preserve Channel Mode (i.e., bit PCHMODE in Global Configuration Descriptor is set),
CX28500 transfers in DATAPTR[1:0] the two MSBs of the channel number and uses bit DATAPTR[2] to signal if this
buffer is the first buffer of a received message (i.e., DATAPTR[2] is set) or not (i.e., DATAPTR[2] is clear). This is
illustrated in
28500-DSH-002-C
25:18
17:15
14
13:0
31:3
2:0
GENERAL NOTE:
Bit
Bit
Field Name
ERROR[2:0]
DLEN[13:0]
CHAN [7.0]
Table
TxLAST
DATAPTR[31:3]
RSVD/
In ECCMODE, Tx/Rx buffer descriptors are 64 bits in length. Therefore, both the BSD and DATAPTR are written after the
buffer is completely processed.
Field Name
Receive Buffer Status Descriptor
Data Buffer Pointer
Don’t Care
NOTE:
Data Buffer Pointer
6-45.
Value
—
—
0
0
1
2
3
4
5
6
7
While CX28500 does support byte addresses for the data, when operating in ECC mode, all
Rx and Tx buffers must be 64-bit aligned. CX28500 assumes the three least significant bits
of the data pointers are 0 regardless of the actual value. However, when updating the buffer
desriptor status, CX28500 preserves the actual value.
Value
When operating in normal mode (i.e., not in Preserve Channel Mode as indicated by bit PCHMODE in
Global Configuration Descriptor) this field is Reserved.
When operating in Preserve Channel Mode (i.e., bit PCHMODE in Global Configuration Descriptor is set0,
this field is used by CX28500 to transfer in it the channel number least 8 significant bits.
OK: No errors detected in this receive buffer.
BUFF: Buffer Error. Data is lost due to Internal data buffer overflow.
COFA: Change Of Frame Alignment. RSYNC signal is misaligned with the flywheel in the serial interface.
OOF: Out Of Frame. ROOF signal is asserted.
ABT: Abort Flag Termination. Received message is terminated with abort sequence, seven sequential
ones, instead of a closing flag (7Eh).
LNG: Long Message. Message payload size greater than selected limit was received. Message processing
is terminated, and transfer to shared memory is discontinued. Channel resumes scanning for HDLC flags
or idle codes.
ALIGN: Octet Alignment Error. Message payload size, after zero extraction, is not multiple of 8 bits. This
error takes precedence over a FCS error.
FCS: Frame Check Sequence Error. Received HDLC frame is terminated with proper 7Eh flag, but
computed FCS does not match received FCS.
Last buffer indicator. Copied from Receive Buffer Descriptor.
Number of received bytes stored by CX28500 in this buffer.
—
—
Table
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6-44, is a 32-bit address to the first byte of a data message in shared
This address points to the first byte of a data buffer.
®
Description
Description
Memory Organization
117