 |
поискавой системы для электроныых деталей |
|
|
поискавой системы для электроныых деталей |
|
DP83261AVF датащи(PDF) 16 Page - National Semiconductor (TI) |
|
|
|
|||||||||||||||||||||||||||||
DP83261AVF датащи(HTML) 16 Page - National Semiconductor (TI) |
|
|
16 / 132 page  50 Functional Description (Continued) In addition to the criteria mentioned above additional crite- ria apply to the servicing of Synchronous and Restricted Requests Synchronous Requests are not serviced if RELRBCNR is set (See Section 451) Restricted requests are not serviced when RELRBCNR RELRCLMR or RELROTRMAC are set (See Section 453) Restricted Dialogues may only begin when a non-restrict- ed token has been received and transmitted (See Sec- tion 453) End of Service Opportunity The Service Opportunity continues until either a token is issued or the ring becomes non-operational A token is issued after the current frame if any is transmit- ted when 1 It is no longer necessary to hold the token All frames of all active requests have been transmitted 2 The token became unusable while servicing a request Asynchronous Priority threshold reached (If an Asynch Priority Request is being serviced) THT expired (if enabled) When the ring becomes non-operational the current frame transmission is aborted The ring may go non-operational while holding a token as a result of any one of the following conditions A MAC Reset Reception of a valid MAC frame TRT expiration (TRT was reset when the token was cap- tured) Issue Token Type The criteria presented to the Ring Engine to begin a Service Opportunity also contains the Issue Token Class The Issue Token Class is used if servicing of that request was com- pleted (the last frame of that request was transmitted) oth- erwise a token of the Capture Token Class is issued When servicing multiple requests on a single service oppor- tunity the Issue Token Class of the previous class becomes the capture class for the next request for purposes of deter- mining usability The type of token issued depends on the service class and the type of token captured as shown in Table 5-2 522 Service Opportunity while Ring Not Operational While the ring is not operational a service opportunity oc- curs if an immediate transmission is requested from the transmitter Data Claim or Beacon State and the transmitter is in the appropriate state The service opportunity continues until any one of the fol- lowing conditions exist 1 No (additional) frames are to be sent 2 TMAX of time elapses on this request 3 The transmitter exits the requested state 4 The ring becomes operational while servicing an immedi- ate request 523 Frame Transmission Frames associated with the current request may be trans- mitted at any time during a Service Opportunity In many applications data is ready to be transmitted when the re- quest is presented to the interface Soon after the Service Opportunity begins frame transmission begins In other ap- plications in order to minimize the effects of ring latency it is desirable to capture the token when no data is ready to be transmitted This capability results in wasted ring bandwidth and should be used judiciously During transmission a byte stream is passed from the Sys- tem Interface to the MAC Request Interface The data is passed through the Ring Engine and appears at the PHY Request Interface two byte times later While a frame is being transmitted the request parameters for the next request (if different) may be presented to the interface At the end of the current frame transmission a decision is made to continue or cancel the current service opportunity based on the new request parameters During a transmission several errors can occur A transmis- sion may be terminated unsuccessfully because of external buffering or interface parity errors internal Ring Engine er- rors a MAC reset or reception of a MAC frame When a transmission is aborted due to an external error (and Op- tionIRPT is not set) a Void frame is transmitted to reset the TVX timers in all stations in the ring When a frame is abort- ed due to a transmission error the Service Opportunity is not automatically ended 53 REQUEST SERVICE PARAMETERS 531 Request Service Class The Request Service corresponds to the Request Service Class and the token class parameters of the (SM )MA DATArequest and (SM )MA Tokenrequest primitives as specified in the Standard 14 useful combinations of the Requested Service Class (Non-Restricted Asynchronous Restricted Asynchronous Synchronous Immediate) the Token Capture and Issue Class and THT Enable are supported by the Ring Engine as shown in Table 5-3 TABLE 5-2 Token Transmission Type Service Class Token Captured Token Issued Non-Restricted Non-Restricted Non-Restricted Begin Restricted Non-Restricted Restricted Continue Restricted Restricted Restricted End Restricted Restricted Non-Restricted Immediate None None Immediate Non-Restricted None Non-Restricted Immediate Restricted None Restricted 16 |
|
ссылки URL |
| Вашему бизинису помогли Аллдатащит? [ DONATE ] |
Что такое Аллдатащит | реклама | контакт | Конфиденциальность | Ссылка на техническое описание | обмен ссыками | поиск по производителю All Rights Reserved©Alldatasheet.com |
| Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
|
Family Site : ic2ic.com |
icmetro.com |
Russian ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
