USB97C102 datasheet(56/80 Pages) SMSC

56 / 80 page

SMSC DS – USB97C102

Page 56

Rev. 03/23/2000

ALTERNATE ADDRESS ENDPOINT MAPPING

This section will describe Endpoint Mapping relative to the Alternate Address registers defined above. Table 102 -

Mapping of External Endpoint Numbers to Internal Endpoint Numbers, on page 56 below, describes the Endpoint

mapping relative to the SIE address embedded in the USB packet. This table describes the mapping of a USB Packet

which is transmitted (USB IN Packet) or received (USB OUT packet) on the USB Bus and is destined for a particular

USB97C102 address. Remember, that the USB97C102 has 4 possible address filters.

The translation is the conversion of the Endpoint Number. The Endpoint Number for OUT packets destined for a

particular address, the Endpoint Number is translated accordingly as defined in Table 102.

Example #1, an OUT packet:

!" If a packet on the USB wire, which contains an address destined for the USB97C102 with a value that matches

Alternate Address #2 (ALT_ADDR2 Register- 0x7F9E) and its endpoint number = 0 and is received, then the

packet header in the MMU contains the Alternate Address #2 address value and an Endpoint Number = 8. The

External Endpoint Number “0” is converted to internal endpoint number “8” for packets directed to alternate

address #2.

Example #2, a IN packet:

!" When the SMSC 97C102 MCU (8051) is building a packet to send to the host, the packet is enqueued onto one

of the 16 Transmit FIFO’s which maps to each Endpoint. In other words, each Endpoint has its own transmit

FIFO. When an IN token is received from the host, that is addressed to alternate address #2 and endpoint 0,

then the SIE pops a packet off of the Tx FIFO for endpoint 8.

As can be seen, endpoint translation is performed for outgoing as well as incoming packets as described in Table

102. Please refer to the SMSC USB97C102 Programmers Reference Guide for additional details.

Multiple Endpoint Mapping

When the SMSC USB97C102 Firmware Developer uses the Alternate Address registers to implement specific device

implementations, internal Endpoints are mapped multiple times relative to the External Endpoint.

Example:

If a packet is received, that is addressed to alternate address #3, then external endpoint numbers 1, 5, 9 and 13 are

all converted to internal endpoint number 13.

Table 102 - Mapping of External Endpoint Numbers to Internal Endpoint Numbers

EXTERNAL EP

(ON THE USB

WIRE)

INTERNAL EP (IN PACKET HEADER)

SIE Addr

Alt Addr 1

Alt Addr 2

Alt Addr 3

EP 0

EP 4

EP 8

EP 12

EP 1

EP 5

EP 9

EP 13

EP 2

EP 6

EP 10

EP 14

EP 3

EP 7

EP 11

EP 15

EP 4

EP 8

EP 12

EP 5

EP 9

EP 13

EP 6

EP 10

EP 14

EP 7

EP 11

EP 15

EP 8

EP 4

EP 8

EP 12

EP 9

EP 5

EP 9

EP 13

EP 10

EP 6

EP 10

EP 14

EP 11

EP 7

EP 11

EP 15

EP 12

EP 4

EP 8

EP 12

EP 13

EP 5

EP 9

EP 13

EP 14

EP 6

EP 10

EP 14

EP 15

EP 7

EP 11

EP 15

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