SL811S/T
Document #: 38-08009 Rev. **
Page 11 of 27
5.3
Endpoint Control Registers
Each endpoint set has a control register defined as follows:
5.3.1
Endpoint Base Address
Pointer to memory buffer location for USB reads and writes.
5.3.2
Endpoint Base Length
The Endpoint Base Length is the maximum packet size for Out transfers from the Host. Essentially, this designates the largest
packet size that can be received by the SL811S/T. For Transfers In to Host, Base Length designates the size of the data packet
to be sent.
5.3.3
Packet Status
The packet status contains information relative to the packet that has been received or transmitted. The register is defined as
follows:
5.3.4
Transfer Count
Contains the number of bytes left over (from ’Length’ field) after a packet is received. If an overflow condition occurs, i.e., the
received packet from host was greater than the Length field, a bit is set in the Packet Status Register indicating the condition.
The user can then determine the number of bytes received greater than the Length field specified by reading this register.
Bit Position
Bit Name
Function
0
Arm
Allows enabled transfers when set =’1’. Clears to '0' when transfer is complete.
1
Enable
When set = '1' allows transfers to this endpoint. When set 0 USB transactions are ignored.
If Enable = '1' and Arm = '0', the endpoint will return NAKs to USB transmissions.
2
Direction
When set = '1' transmit to Host. When '0', receive from Host.
3
Next Data Set
'0' if next data set is ‘a’, '1' if next data set is 'b'
4
ISO
When set to '1' allows Isochronous mode for this endpoint.
5
Send STALL
When set to ‘1’ sends Stall in response to next request on this endpoint.
6
Sequence
Sequence Bit. '0' if DATA0, '1' if DATA1.
7
Reserved
Bit Position
Bit Name
Function
0
ACK
Transmission Acknowledge.
1
Error
Error detected in transmission.
2
Time-out
Time-out occurred.
3
Sequence
Sequence Bit. '0' if DATA0, '1' if DATA1.
4
Setup
'1' indicates Setup Packet
5
Overflow
Overflow condition - maximum length exceeded during receives.
6
NAK
Slave returns NAK
7
STALL
Slave set STALL bit
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