38.15.2 Packet Size

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


Bit	31	30	29	28	27	26	25	24
	AUTO_ZLP	SIZE[2:0]			MULTI_PACKET_SIZE[13:10]
Access	R/W	R/W	R/W	R/W	R/W	R/W	R/W	R/W
Reset	x	0	0	x	0	0	0	0


Bit	23	22	21	20	19	18	17	16
	MULTI_PACKET_SIZE[9:2]
Access	R/W	R/W	R/W	R/W	R/W	R/W	R/W	R/W
Reset	0	0	0	0	0	0	0	0


Bit	15	14	13	12	11	10	9	8
	MULTI_PACKET_SIZE[1:0]		BYTE_COUNT[13:8]
Access	R/W	R/W	R/W	R/W	R/W	R/W	R/W	R/W
Reset	0	x	0	0	0	0	0	0


Bit	7	6	5	4	3	2	1	0
	BYTE_COUNT[7:0]
Access	R/W	R/W	R/W	R/W	R/W	R/W	R/W	R/W
Reset	0	0	0	0	0	0	0	x

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.

Value	Description
0	Automatic Zero Length Packet is disabled.
1	Automatic Zero Length Packet is enabled.

Bits 30:28 – SIZE[2:0] Endpoint size

These bits contains the maximum packet size of the endpoint.


Value	Description
0x0	8 Byte
0x1	16 Byte
0x2	32 Byte
0x3	64 Byte
0x4	128 Byte⁽¹⁾
0x5	256 Byte⁽¹⁾
0x6	512 Byte⁽¹⁾
0x7	1023 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.