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поискавой системы для электроныых деталей |
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поискавой системы для электроныых деталей |
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DP83261AVF датащи(PDF) 17 Page - National Semiconductor (TI) |
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DP83261AVF датащи(HTML) 17 Page - National Semiconductor (TI) |
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17 / 132 page  50 Functional Description (Continued) TABLE 5-3 Request Service Classes RQRCLS Name Class THT Token Token Notes Capture Issue 0000 None None 0001 Apri 1 Async Enabled Non-rstr Non-rstr THSH1 0010 Reserved Reserved 0011 Reserved Reserved 0100 Syn Synch Disabled Any Captured 1 0101 Imm Immediate Disabled None None 4 0110 ImmN Immediate Disabled None Non-rstr 4 0111 ImmR Immediate Disabled None Rstr 4 1000 Asyn Asynch Enabled Non-rstr Non-rstr 1001 Rbeg Restricted Enabled Non-rstr Rstr 2 3 1010 Rend Restricted Enabled Rstr Non-rstr 2 1011 Rcnt Restricted Enabled Rstr Rstr 2 1100 AsynD Asynch Disabled Non-rstr Non-rstr 1101 RbeginD Restricted Disabled Non-rstr Rstr 2 3 1110 RenD Restricted Disabled Rstr Non-rstr 2 1111 RcntD Restricted Disabled Rstr Rstr 2 Note 1 Synchronous Requests are not serviced when bit BCNR of the Ring Event Latch Register is set Note 2 Restricted Requests are not serviced when bit BCNR CLMR or OTRMAC of the Ring Event Latch Register is set Note 3 Restricted Dialogues only begin when a Non-Restricted token has been received and transmitted Note 4 Immediate Requests are serviced when the ring is Non-Operational These requests are serviced from the Data state if neither signal RQCLM nor RQBCN is asserted If signal RQCLM is asserted Immediate Requests are serviced from the Claim State If signal RQBCN is asserted Immediate Requests are serviced from the Beacon State RQCLM and RQBCN do not cause transitions to the Claim and Beacon States Requests are serviced on a Service Opportunity meeting the requested criteria External support is required to limit the requests presented to the MAC Interface by different MAC Users (SMT LLC etc) A Token Capture Class of non-rstr indicates that the Trans- mitter Token Class must be Non-Restricted to begin servic- ing the request A Token Capture Class of rstr indicates that the Transmitter Token Class must be Restricted to be- gin servicing the Request A Token Issue Class of non-rstr means that the Transmitter Token Class will be Non-Re- stricted upon completion of the request A Token Issue Class of rstr means that the Transmitter Token Class will be Restricted upon completion of the request 532 Request Options The Request Options provide the ability for Source Address Transparency (SAT) and FCS Transparency (FCST) In both cases data from the request stream is transmitted in place of data from either the Ring Engine The use of Source Ad- dress transparency has no effect on the sequencing of the interface When Source Address transparency is not used the SA from the internal parameter RAM is substituted for the SA bytes in the request stream which must still be pres- ent Since the FCS is appended to the frame when FCS transparency is not used no FCS bytes are present in the request stream Source Address Transparency Normally the SA field in a frame is generated by the BMAC device using either the MSA or MLA When the SA Trans- parency option is selected the SA from the data stream is transmitted in place of the MSA or MLA The SAT option can be invoked on a per frame basis upon the assertion of the SAT signal (Pin 12) When the SA Transparency option is selected it is neces- sary to rely on an alternate stripping mechanism because stripping based on the returning SA only guarantees that frames with MSA or MLA will be stripped Either the Void Stripping option (described below) may be invoked or exter- nal hardware that forces stripping using the EM (External M Flag) signal is required The MSB of the SA is not controlled by this option It is normally forced to Zero It can be controlled using the Source Address MSB Transparency option described be- low SA Transparency is possible for all frames (including MAC frames) External support is required to limit the use of SA Transparency to certain MAC Users SA Transparency should not be used with externally generated MAC Frames in order to maintain accountability but this is not enforced by the Ring Engine 17 |
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