EZ-USB Datasheet, PDF (160/334 Pages) Cypress Semiconductor – The EZ-USB USB Integrated Circuit

times 19 cycles, or 2,432 cycles. The 1,024 byte transfer would take 403 µs, less than
half of the 1-ms USB frame time.
If still faster time is required, the routine can be modified to put more of the MOVX
instructions in-line. For example, with 16 in-line MOVX instructions, the transfer time
for 1,024 bytes would be 35 cycles times 64 loops or 2,240 cycles, or 371 µs, an 8% speed
improvement over the eight instruction loop.
8.9 Other Isochronous Registers
Two additional registers, ISOCTL and ZBCOUT, provide additional isochronous endpoint
features.
8.9.1 Disable ISO
ISOCTL
b7
b6
-
-
Isochronous Control
b5
b4
b3
b2
-
-
PPSTAT
MBZ
Figure 8-14. ISOCTL Register
7FA1
b1
MBZ
b0
ISODISAB
Bit zero of the ISOCTL register is called ISODISAB. When the 8051 sets ISODISAB=1,
all sixteen of EZ-USB endpoints are disabled. If ISODISAB=1, EP8IN=EP15IN and
EP8OUT-EP15OUT should not be used. ISODISAB is cleared at power-on.
When ISODISAB=1, the 2,048 bytes of RAM normally used for isochronous buffers is
available to the 8051 as XDATA RAM (not program memory), from 0x2000 to 0x27FF in
internal memory. When ISODISAB=1, the behavior of the RD# and WR# strobe signals
changes to reflect the additional 2 KB of memory inside the EZ-USB chip. This is shown
in Table 8-2.
Table 8-2. Addresses for RD# and WR# vs. ISODISAB bit
ISODISAB RD#, WR#
0
2000-7B40,
(default) 8000-FFFF
1
2800-7B40,
8000-FFFF
EZ-USB TRM v1.9
Chapter 8. EZ-USB CPU
Page 8-15