28.5.4 Endpoint Control
| Name: | CTRL |
| Offset: | 0x01 + n*0x08 [n=0..1] |
| Reset: | 0x00 |
| Bit | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | |
| TYPE[1:0] | MULTIPKT | AZLP | TCDSBL | DOSTALL | BUFSIZE[1:0] | ||||
| Access | R/W | R/W | R/W | R/W | R/W | R/W | R/W | R/W | |
| Reset | x | x | x | x | x | x | x | x | |
Bits 7:6 – TYPE[1:0] Endpoint Type
These bits enable and select the endpoint type. If the endpoint is disabled, the remaining seven endpoint configuration bytes are never read or written by the USB peripheral, and their RAM locations are free to use for other application data.
| Value | Name | Description |
|---|---|---|
| 0x0 | DISABLE | Endpoint Disabled |
| 0x1 | CONTROL | Control |
| 0x2 | BULKINT | Bulk or Interrupt |
| 0x3 | ISOCHRONOUS | Isochronous |
Bit 5 – MULTIPKT Multi-packet Transfer Enable
Writing this bit to ‘1’ enables multi-packet transfers.
The multi-packet transfer enables a data payload exceeding the maximum
packet size of an endpoint to be transferred as multiple packets
without interrupts or firmware intervention. When MULTIPKT is
‘1’, MCNT defines the maximum size of a single
OUT packet, thereby preventing the data reception buffer overrun.
Bit 4 – AZLP Automatic Zero Length Packet
Writing this bit to ‘1’ allows the USB peripheral
to manage a transaction complete signaling with ZLP, without
firmware interaction. When Multi-packet Transfer Enable
(MULTIPKT) is disabled, this bit has no effect. The behavior
depends on the transfer direction:
IN: An ZLP is automatically sent if the last data packet of a multi-packet transfer is equal to ep_size.
OUT: If the last packet of a multi-packet transfer was equal to ep_size, the Transaction Complete (TRNCOMPL) flag and interrupt will be set by the next ZLP.
Bit 3 – TCDSBL TRNCOMPL Interrupt Disable
When this bit is written to ‘1’, the Transaction
Complete (TRNCOMPL) flag in the Interrupt Flags B (INTFLAGSB) register
is not set together with the TRNCOMPL flag of the endpoint in the
Endpoint Status (EPn.STATUS) register. The FIFO will not store the
endpoint configuration table address for this endpoint until
transaction completes, if TCDSBL is ‘1’.
Bit 2 – DOSTALL Endpoint Will Respond with STALL
When this bit is written to ‘1’, the USB
controller will respond to IN or OUT transactions with a STALL
handshake. No STALL will be sent if the endpoint is a control
endpoint and the Endpoint Setup (EPSETUP) bit in the EPn STATUS
register is ‘1’. DOSTALL is direction-specific,
i.e., IN transactions are stalled if IN.CTRL.DOSTALL is set and
OUT transactions are stalled if OUT.CTRL.DOSTALL is set.
STATUS.EPSETUP for control IN endpoints can override CTRL.DOSTALL, ensuring that the device will not STALL the data or the status stage of a control transfer before the CPU has had time to process the request, in case CTRL.DOSTALL was set from the previous request.
Bits 1:0 – BUFSIZE[1:0] Data Size (Default)
This bit field configures the maximum data payload size for the endpoint. Incoming data bytes exceeding the maximum data payload size are discarded. For control endpoints, this field only affects IN and OUT transactions. For SETUP transaction, the maximum data payload is always of eight bytes.
| Value | Name | Description |
|---|---|---|
| 0x0 | DEFAULT_BUF8 | 8 bytes buffer size |
| 0x1 | DEFAULT_BUF16 | 16 bytes buffer size |
| 0x2 | DEFAULT_BUF32 | 32 bytes buffer size |
| 0x3 | DEFAULT_BUF64 | 64 bytes buffer size |