cx28500 Mindspeed Technologies, cx28500 Datasheet - Page 146

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

8.2.3
At least seven consecutive 1s constitute an abort code. Receiving the abort code causes the current frame
processing to be aborted, and further data transfer into shared memory for that message is terminated. After
detecting the abort code, CX28500 enters a scan mode, which searches for a new opening flag character.
Notification of this detected condition is provided by the receive buffer status descriptor and/or an interrupt
descriptor indicating the error condition Abort Flag Termination.
In cases where received idle codes transition to an abort code, an interrupt descriptor is generated toward the Host
(if enabled in
discarded.
In the transmission direction, an ABORT code’s handling is depended on what the user tells CX28500 to do. An
ABORT code could just abort the transmission of the current message, or it can mean aborting the current
message transmission and then starting transmitting the next message, if it exists.
8.2.4
CX28500 provides zero-bit insertion and deletion when it encounters five consecutive 1s within a frame. In the
receiver, the zero bit is removed (discarded). In the transmitter, the zero bit is inserted after each sequence of five
ones. Zero-bit insertion, or bit-stuffing, is only done in the message section and not in the pad fill section.
8.2.5
The Transmit Buffer Descriptor contains message configuration bits to specify what data pattern is transmitted after
the end of a current message and its respective closing flag have been transmitted. The bits are specified as
follows:
•
•
•
8.2.5.1
The Idle Code (IC) specification allows one of a set of idle codes to be chosen to be transmitted after the current
message in case the next message is not available to be transmitted or inter-message pad fill is requested via
PADCNT. The default Idle Code for HDLC mode is flag, or 7Eh.
8.2.5.2
The Pad Count (PADCNT) specification allows pad fill octets (a sequence of one or more specified idle codes) to
be transmitted between messages. PADCNT is the minimum number of fill octets to be transmitted between closing
flag of one message and the opening flag of the next message in the following manner:
28500-DSH-002-C
Idle Code specification, IC
Inter-message Pad Fill Count, PADCNT
Send an Abort Sequence, ABORT
Section
NOTE:
NOTE:
Abort Codes
Zero-Bit Insertion/Deletion
Message Configuration Bits–HDLC Mode
Idle Code
Inter-Message Pad Fill
6.6.2), indicating the informational event Change To Abort Code. All received abort codes are
Seven ones are the abort condition CX28500 checks for while receiving a message, but the
criteria for detection and generation of a Change To Abort Code interrupt is equal to 14
consecutive ones.
Message configuration bits are also used in Transparent mode with slightly different
meanings. For details see
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Section
8.3.1.
®
Basic Operations
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