13.25.8.4.3 Packet Size

Name: PCKSIZE
Offset: 0x04 & 0x14
Reset: 0xxxxxxxxx
Property: NA

Bit 3130292827262524 
 AUTO_ZLPSIZE[2:0]MULTI_PACKET_SIZE[13:10] 
Access R/WR/WR/WR/WR/WR/WR/WR/W 
Reset x00x0000 
Bit 2322212019181716 
 MULTI_PACKET_SIZE[9:2] 
Access R/WR/WR/WR/WR/WR/WR/WR/W 
Reset 00000000 
Bit 15141312111098 
 MULTI_PACKET_SIZE[1:0]BYTE_COUNT[13:8] 
Access R/WR/WR/WR/WR/WR/WR/WR/W 
Reset 0x000000 
Bit 76543210 
 BYTE_COUNT[7:0] 
Access R/WR/WR/WR/WR/WR/WR/WR/W 
Reset 0000000x 

Bit 31 – AUTO_ZLP Automatic Zero Length Packet

This bit defines the automatic Zero Length Packet mode of the endpoint.

When enabled, the USB module will manage the ZLP handshake by hardware. This bit is for IN endpoints only. When disabled the handshake should be managed by firmware.

ValueDescription
0Automatic Zero Length Packet is disabled.
1Automatic Zero Length Packet is enabled.

Bits 30:28 – SIZE[2:0] Endpoint size

These bits contains the maximum packet size of the endpoint.

ValueDescription
0x08 Byte
0x116 Byte
0x232 Byte
0x364 Byte
0x4128 Byte(1)
0x5256 Byte(1)
0x6512 Byte(1)
0x71023 Byte(1)
(1) for Isochronous endpoints only.

Bits 27:14 – MULTI_PACKET_SIZE[13:0] Multiple Packet Size

These bits define the 14-bit value that is used for multi-packet transfers.

For IN endpoints, MULTI_PACKET_SIZE holds the total number of bytes sent. MULTI_PACKET_SIZE should be written to zero when setting up a new transfer.

For OUT endpoints, MULTI_PACKET_SIZE holds the total data size for the complete transfer. This value must be a multiple of the maximum packet size.

Bits 13:0 – BYTE_COUNT[13:0] Byte Count

These bits define the 14-bit value that is used for the byte count.

For IN endpoints, BYTE_COUNT holds the number of bytes to be sent in the next IN transaction.

For OUT endpoint or SETUP endpoints, BYTE_COUNT holds the number of bytes received upon the last OUT or SETUP transaction.