Table 17-34. Outmaxp Register; Table 17-35. Outmaxp Fields; Out Maximum Packet Size Register Ep 1 And 2 (Outmaxp) - Sharp LH79524 User Manual

Universal Serial Bus Device

17.2.3.6 OUT Maximum Packet Size Register EP 1 and 2 (OUTMAXP)

OUTMAXP is programmed with the maximum packet size for transactions through the cur-
rently-selected OUT endpoint — in units of 8 bytes, except that a value of 128 sets the
maximum packet size to 1023 (the maximum size for an isochronous packet) rather than
1024. In setting this value, note the constraints placed by the USB Specification on packet
sizes for Bulk, Interrupt and Isochronous transactions in Full-speed operations.
The value written to this register should match the wMaxPacketSize field of the Standard
Endpoint Descriptor for the associated endpoint (see Universal Serial Bus Specification
Revision 2.0, Chapter 9). A mismatch could cause unexpected results.
The total amount of data represented by the value written to this register must not exceed
the FIFO size for the OUT endpoint, and should not exceed half the FIFO size if double-
buffering is required. If a value greater than the OUT FIFO size (see Table 17-2) for the
endpoint is written to this register, the value will be automatically changed to the OUT FIFO
size. If the value written to this register is less than or equal to half the OUT FIFO size, two
OUT packets can be buffered.
BIT
FIELD
RESET
RW
BIT
FIELD
RESET
TYPE
ADDR
BITS
31:8
7:0
17-26

Table 17-34. OUTMAXP Register

31 30 29 28 27
0 0 0 0 0
RO RO RO RO RO
15 14 13 12 11
///
0 0 0 0 0
RO RO RO RO RO
(with the INDEX register set to OUT endpoint 1 or 2)

Table 17-35. OUTMAXP Fields

NAME
/// Reserved Reading returns 0. Write the reset value.
OUTMAXP OUT Maximum Packet Size Maximum Packet Size/transaction
26 25 24 23
///
0 0 0 0
RO RO RO RO
10 9 8 7
0 0 0 0
RO RO RO RW
0xFFFF5000 + 0x04C
Version 1.0
LH79524/LH79525 User's Guide
22 21 20 19
0 0 0 0
RO RO RO RO RO
6 5 4 3
OUTMAXP
0 0 0 0
RW RW RW RW RW
FUNCTION
18 17 16
0 0 0
RO RO
2 1 0
0 0 0
RW RW