dp83261 National Semiconductor Corporation, dp83261 Datasheet - Page 93

• Manufacturer Part Number: dp83261
• Description: Bmac Device Fddi Media Access Controller
• Manufacturer: National Semiconductor Corporation

RQRCLS(3 – 0)
RQCLM
RQBCN
Symbol
STRIP
SAT
SAIGT
FCST
7 0 Signal Descriptions
Service Parameters
The Service Parameters define the Service Request They must be valid for at least one byte time before the RQRDY signal is
asserted and must not change while RDRDY remains asserted See Section 5 3 1 for the encoding of RQRCLS
The Requested Service corresponds to the Request Service Class and the Token Class parameters of the
(SM )MA DATA request and (SM )MA Token request primitives as specified in the Standard
Encoded into each of the 14 possible values of RQRCLS in the Service Class (Non-Restricted Asynchronous Restricted
Asynchronous Synchronous Immediate) the Token Capture and Issue Class and THT Enable
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 )
Frame Options
The Frame Options signals are selected for each frame They must be valid while the RQSEND signal is asserted These
options are typically used in bridging applications
Symbol
Pin
13
12
11
14
19 – 22
Pin
15
16
I O
I
I
I
I
Void Strip Forces two My Void frames to be transmitted on end of current Service Opportunity
Stripping continues until a My Void frame returns If any frame of a Service Opportunity requests this
option then all frames on that Service Opportunity will be stripped using this method
Source Address Transparency When SA transparency is selected the SA from the data stream is
transmitted in place of the internal MSA or MLA stored in the MAC Parameter RAM
Source Address I G Transparency With this option the MSB of the SA is sourced from the data
stream as opposed to being forced to zero
Frame Check Sequence Transparency When selected the Ring Engine generated FCS is not
appended to the end of the Information field
I O
I
I
I
Request Class Indicates the Service Class parameters for this request (see Section 5 3 1)
When RQRCLS
and assert TXRDY The Service Opportunity continues as long as the token is usable with the
current service parameters even if RQRDY is not asserted If RQRCLS indicates a service class
that is not serviceable for any cycle of a service opportunity the service opportunity will conclude
after the current frame and a token of the issue token class will be issued
If RQRCLS
issued (even if RQRCLS subsequently becomes non-zero) See Table 5-3
Request Claim Indicates that this request is to be serviced in the Claim state Ignored for non-
immediate requests
Request Beacon Indicates that this request is to be serviced in the Beacon state Ignored for
non-immediate requests
(Continued)
e
0 the Service Opportunity will terminate after the current frame and a token will be
l
0 the Transmitter will capture a usable token (for non-immediate requests)
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Description
Description