Endpoint Control Registers

Endpoint Control Registers

The Endpoint Control registers contain the endpoint control bits for the 16 endpoints available on USB for a decoded address. These four bits define all the control necessary for any one endpoint. Endpoint 0 (ENDPT0) is associated with control pipe 0, which is required by USB for all functions. Therefore, after receiving a USB_RST interrupt, the microprocessor sets ENDPT0 to contain 0Dh.

Table 4-21. Endpoint Control Registers

 

BIT

 

7

6

5

 

4

3

 

2

1

0

 

OFFSET

 

 

 

 

 

11h through 7h

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

FIELDS

 

WOHOST_ _HUB

RETRY_DIS

///

 

CTLEP__DIS

RXEP__EN

 

TXEP__EN

STALLEP_

HSHKEP_

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

RESET

 

0

0

0

 

0

0

 

0

0

0

 

RW

 

R/W

R/W

R/W

 

R/W

R/W

 

R/W

R/W

R/W

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 4-22. Endpoint Control Register Definitions

 

 

 

 

 

 

 

 

Bits

 

Field Name

 

 

Description

 

7

 

HOST_WO_HUB

 

 

Host-Mode-Only Bit

 

 

 

 

 

 

A host-mode-only bit that is present only in the Control register for endpoint 0

 

 

 

 

 

 

(endpt0_rg).

 

 

 

 

 

 

1 = host can communicate to a directly connected low-speed device.

 

 

 

 

 

 

0 = host produces the PRE_PID, then switches to low-speed signaling to send a

 

 

 

 

 

 

token to a low-speed device. This is required to communicate with a low-speed

 

 

 

 

 

 

device through a hub.

 

6

 

RETRY_DIS

 

 

Host-Mode-Only Bit

 

 

 

 

 

 

A host-mode-only bit that is present only in the control register for endpoint 0

 

 

 

 

 

 

(endpt0_rg).

 

 

 

 

 

 

1 = prevent host retrying NAK’ed transactions. When a transaction is NAK'ed, the

 

 

 

 

 

 

NAK PID updates the BDT PID field and the token-done interrupt is set.

 

 

 

 

 

 

(Required setting when host tries to poll an interrupt endpoint.)

 

 

 

 

 

 

0 = NAK'ed transactions are retried in hardware.

 

5

///

 

 

Reserved

 

4

 

EP_CTL_ DIS

 

 

Endpoint Enable

 

3

 

EP_RX_EN

 

 

Defines whether an endpoint is enabled and the direction of the endpoint. Table

 

2

 

EP_TX_EN

 

 

4-23shows the enable/direction control values.

 

 

 

 

 

 

1

 

EP_STALL

 

 

Endpoint Stalled

 

 

 

 

 

 

This bit has priority over all control bits in the Endpoint Enable register; however,

 

 

 

 

 

 

it is only valid if EP_IN_EN=1 or EP_OUT_EN=1. Any access to this endpoint

 

 

 

 

 

 

causes the USB to return a STALL handshake. After an endpoint stalls, it requires

 

 

 

 

 

 

intervention from the host controller.

 

0

 

EP_HSHK

 

 

Endpoint Handshaking

 

 

 

 

 

 

1 = defines whether the endpoint performs handshaking during a transaction to

 

 

 

 

 

 

this endpoint

 

 

 

 

 

 

This bit is generally set, unless it is an isochronous endpoint.

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Lantronix DSTni-EX manual 21. Endpoint Control Registers, 22. Endpoint Control Register Definitions, Host-Mode-Only Bit