9.3.6.10 RX_MAX_P_REG Bit Definitions
| Bit Number | Name | Reset Value | Function |
|---|---|---|---|
| [15:11] | m-1 | N/A | If the core is configured for high-bandwidth
ISO/interrupt endpoints or packet splitting on bulk endpoints, the register
includes either 2 or 5 further bits that define a multiplier m, which is equal
to one more than the value recorded. For bulk endpoints with the packet splitting option enabled, the multiplier m can be up to 32 and defines the number of USB packets of the specified payload which are to be amalgamated into a single data packet within the FIFO. If the packet splitting option is not enabled, bits[15:13] are not implemented and bits[12:11] (if included) are ignored. For ISO/interrupt endpoints operating in High speed mode and with the high-bandwidth option enabled, m may only be either 2 or 3 (corresponding to bit 11 set or bit 12 set) and it specifies the maximum number of such transactions that can take place in a single microframe. If either bit[11] or bit[12] is non-zero, the USB controller automatically combines the separate USB packets received in any microframe into a single packet within the receive FIFO. The maximum payload for each transaction is 1,024 bytes, so this allows up to 3,072 bytes to be received in each microframe. For ISO transfers in Full speed mode or if high-bandwidth is not enabled, bits[11] and [12] are ignored. The value written to bits[10:0] (multiplied by m in the case of high-bandwidth ISO transfers) must match the value given in the wMaxPacketSize field of the standard endpoint descriptor for the associated endpoint (see the USB specification revision 2.0, A mismatch could cause unexpected results. The total amount of data represented by the value written to this register (specified payload × m) must not exceed the FIFO size for the receive endpoint, and should not exceed half the FIFO size if double-buffering is required. |
| [10:0] | RxMaxP | 0 | Maximum payload/transaction. Maximum payload
in bytes received in a single transaction. The value set can be up to 1,024
bytes but is subject to the constraints placed in the USB specification on
packet sizes for bulk, interrupt, and ISO transfers in full speed and high
speed operations. RxMaxP must be set to an even number of bytes for proper interrupt generation in DMA mode 1. |