EZ-USB Datasheet, PDF (185/334 Pages) Cypress Semiconductor – The EZ-USB USB Integrated Circuit

Table 10-2. EZ-USB States After a USB Bus Reset
Item
Register
1 Endpt Data
2 Byte Counts
3 CPUCS
4 PORT Configs
5 PORT Registers
6 PORT OEs
7 Interrupt Enables
8 Interrupt Reqs
9 Bulk IN C/S
10 Bulk OUT C/S
11 Toggle Bits
12 USBCS
13 FNADDR
14 IN07VAL
15 OUT07VAL
16 INISOVAL
17 OUTISOVAL
18 USBPAIR
19 Configuration
20 Alternate Setting
Default
Value
Comment
uuuuuuuu u = unchanged
uuuuuuuu
uuuuuuuu
uuuuuuuu
uuuuuuuu
uuuuuuuu
uuuuuuuu
uuuuuuuu
00000000 unarm
uuuuuuuu retain armed/unarmed state
00000000
uuuuuuuu ReNum bit unchanged
00000000 USB Function Address
uuuuuuuu
uuuuuuuu
uuuuuuuu
uuuuuuuu
uuuuuuuu
0
0
A USB bus reset leaves most EZ-USB resources unchanged. From Table 10-2, after USB
bus reset:
• The EZ-USB core unarms all Bulk IN endpoints (9). Data loaded by the 8051 into
an IN endpoint buffer remains there, and the 8051 firmware can either re-send it by
loading the endpoint byte count register to re-arm the transfer, or send new data by
re-loading the IN buffer before re-arming the endpoint.
• Bulk OUT endpoints retain their busy states (10). Data sent by the host to an OUT
endpoint buffer remains in the buffer, and the 8051 firmware can either read the
data or reject it as stale simply by not reading it. In either case, the 8051 loads a
dummy value to the endpoint byte count register to re-arm OUT transfers.
• Toggle bits are cleared (11).
• The device address is reset to zero (13).
Page 10-6
Chapter 10. EZ-USB Resets
EZ-USB TRM v1.9