Sharp LH79524 - IN Maximum Packet Size Register (INMAXP); Table 17-26. INMAXP Register; Table 17-27. INMAXP Fields

Universal Serial Bus Device LH79524/LH79525 User’s Guide
17-20 Version 1.0
17.2.3.2 IN Maximum Packet Size Register (INMAXP)
INMAXP defines the maximum packet size for transactions through the currently-selected
IN endpoint in units of 8 bytes, except that a value of 128 sets the maximum packet size
to 1,023 (the maximum size for an Isochronous packet transferred in a Full-speed trans-
action) rather than 1,024. When setting this value, note the constraints placed by the USB
Specification on packet sizes for Bulk, Interrupt, and Isochronous transactions in Full-
speed operations.
There is an INMAXP register for each IN endpoint, except Endpoint 0. Each register is
accessed via the INDEX register. For example, to access EP1 INMAXP register, write 0x1
to the INDEX register and then write the data required to address INMAXP (0x40).
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 may cause unexpected results. If a value greater
than the IN FIFO (see Table 17-2) size for the endpoint is written to this register, the value
will be automatically changed to the IN FIFO size. If the value written to this register is less
than or equal to half the IN FIFO size, two IN packets can be buffered. The register is reset
to 0. If this register is changed after packets have been sent from the endpoint, the end-
point IN FIFO should be flushed (using INCSR1:FIFO_FLUSH) after writing the new value
to the INMAXP register.
Table 17-26. INMAXP Register
BIT 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
FIELD ///
RESET 0000000000000000
RW RO RO RO RO RO RO RO RO RO RO RO RO RO RO RO RO
BIT 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
FIELD /// INMAXP
RESET 0000000000000000
TYPE RO RO RO RO RO RO RO RO RW RW RW RW RW RW RW RW
ADDR
0xFFFF5000 + 0x040
(with the INDEX register set to IN endpoint 1, 2, or 3)
Table 17-27. INMAXP Fields
BITS NAME FUNCTION
31:8
/// Reserved Reading returns 0. Write the reset value.
7:0 INMAXP IN Maximum Packet Size Maximum Packet Size/transaction