DP83266 datasheet(9/152 Pages) NSC

9 / 152 page

30 Architectural Description (Continued)

Confirmation Messages (CNFs) are created by the MACSI

device to record the result of a Request operation

Pool Space Descriptors (PSPs) describe the location and

size of a region of memory space available for writing Input

Data Units

Request (transmit) and Indicate (receive) data structures

are summarized in

Figure 3-3

332 Descriptor Queues and Lists

The MACSI device uses 10 Queues and two Lists which are

circular There are six Queues for Indicate operations and

four Queues and two Lists for Request operations Each of

the three Indicate Channels has a Data Queue containing

Pool Space Descriptors (PSPs) and a Status Queue con-

taining Input Data Unit Descriptors (IDUDs) Each Request

Channel has a Data Queue containing Request Descriptors

(REQs) a Status Queue containing Confirmation Messages

(CNFs) and a List containing Output Data Unit Descriptors

(ODUDs)

During Indicate and Request operations Descriptor Queues

and Lists are read and written by the MACSI device using

registers in the Pointer and Limit RAM Register files The

Pointer RAM Queue and List Pointer Registers point to a

location from which a Descriptor will be read (PSPs and

REQs) or written (IDUDs and CNFs) All of the Queues and

Lists are strictly unidirectional The MACSI consumes ob-

jects in those queues which are produced by the Host The

Host consumes objects in those queues which are pro-

duced by the MACSI

For each Queue Pointer Register there is a corresponding

Queue Limit Register in the Limit RAM Register file which

holds the Queue’s limit as an offset value in units of 1 De-

scriptor (8 bytes) The address in the Queue Pointer is incre-

mented before a Descriptor is read and after a Descriptor is

written then compared with the value in the corresponding

Queue Limit Register When a Queue Pointer Register be-

comes equal to the Queue Limit Register an attention is

generated informing the host that the Queue is empty

When a pointer value is incremented past the end of the

page it wraps to the beginning of the page

333 Storage Allocation

The maximum unit of contiguous storage allocation in exter-

nal memory is a Page All MACSI device addresses consist

of a 16-bit page number and a 12-bit offset

The MACSI device uses a page size of 1 kByte or 4 kBytes

for storage of Descriptor Queues and Lists (as selected by

the user) and a page size of 4 kBytes for storage of Data

Units A single page may contain multiple Data Units and

multiple-part Data Units may span multiple disjoint or con-

tiguous pages

34 SERVICE ENGINE

The Service Engine which manages the operation of the

MACSI contains seven basic blocks Indicate Machine Re-

quest Machine StatusSpace State Machine Pointer RAM

Limit RAM and Bus Interface Unit An internal block dia-

gram of the Service Engine is shown in

Figure 3-4

341 Indicate Machine

The Indicate Block accepts Service Data Units (frames)

from the Ring Engine (MAC) in a byte stream format

(MA

Indicate)

DP83266 Datasheet(PDF) 9 Page - National Semiconductor (TI)

DP83266 Datasheet(HTML) 9 Page - National Semiconductor (TI)

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL