Cypress EZ-USB Series 2100 Service Manual Page 144

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EZ-USB TRM v1.9 Chapter 7. EZ-USB CPU Page 7-23
7.3.12 Firmware Load
The USB endpoint zero protocol provides a mechanism for mixing vendor-specific
requests with the previously described standard device requests. Bits 6:5 of the bmRe-
quest field are set to 00 for a standard device request, and to 10 for a vendor request.
The EZ-USB core responds to two endpoint zero vendor requests, RAM Download and
RAM Upload. These requests are active in all modes (ReNum=0 or 1).
Because bit 7 of the first byte of the SETUP packet specifies direction, only one bRequest
value (0xA0) is required for the upload and download requests. These RAM load com-
mands are available to any USB device that uses the EZ-USB chip.
A host loader program typically writes 0x01 to the CPUCS register to put the 8051 into
RESET, loads all or part of the EZ-USB internal RAM with 8051 code, and finally reloads
the CPUCS register with 0 to take the 8051 out of RESET. The CPUCS register is the
only USB register that can be written using the Firmware Download command.
Table 7-21. Firmware Download
Byte Field Value Meaning 8051 Response
0 bm Request Type 0x 40 Vendor Request, OUT
None required
1 bRequest 0xA0 “Firmware Load”
2 wValueL AddrL Starting address
3 wValueH AddrH
4 wIndexL 0x00
5 wIndexH 0x00
6 wLengthL LenL Number of bytes
7 wLengthH LenH
Table 7-22. Firmware Upload
Byte Field Value Meaning 8051 Response
0 bm Request Type 0xC0 Vendor Request, IN
None Required
1 bRequest 0xA0 “Firmware Load”
2 wValueL AddrL Starting address
3 wValueH AddrH
4 wIndexL 0x00
5 wIndexH 0x00
6 wLengthL LenL Number of Bytes
7 wLengthH LenH
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