Cypress Semiconductor FX2LP Información técnica Pagina 58

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EZ-USB FX2 Technical Reference Manual
Page 2-4 EZ-USB FX2 Technical Reference Manual v2.1
must always be accepted and never NAK’d. It is possible, therefore, that a CONTROL transfer
could arrive while the firmware is still servicing a previous one. In this case, the earlier CONTROL
transfer service should be aborted and the new one serviced. The SUTOK interrupt gives advance
warning that a new CONTROL transfer is about to overwrite the eight SETUPDAT bytes.
If the firmware stalls endpoint zero (by setting the STALL and HSNAK bits to 1), the FX2 automat-
ically clears the stall bit when the next SETUP token arrives.
Like all FX2 interrupt requests, the SUTOK and SUDAV bits can be directly tested and cleared by
the firmware (cleared by writing 1) even if their corresponding interrupts are disabled.
Figure 2-3 shows the FX2 registers that are associated with CONTROL transactions over EP0.
Figure 2-3. Registers Associated with EP0 Control Transfers
These registers augment those associated with normal bulk transfers over endpoint zero, which
are described in Chapter 8, "Access to Endpoint Buffers".
Two bits in the USBIE (USB Interrupt Enable) register enable the SETUP Token (SUTOK) and
SETUP Data Available interrupts. The actual interrupt-request bits are in the USBIRQ (USB Inter-
rupt Requests) register.
The FX2 transfers the eight SETUP bytes into eight bytes of RAM at SETUPDAT. A 16-bit pointer,
SUDPTRH:L, provides hardware assistance for handling CONTROL IN transfers, in particular the
Get Descriptor
requests described later in this chapter.
8 Bytes of
SETUP Data
Interrupt Enable:
Initialization
SETUPDAT
Data transfer
Registers Associated with Endpoint Zero
For handling SETUP transactions
7 6 5 4 3 2 1 0
EP0BCL
15 14 13 12 11 10 9 8
EP0BCH
15 14 13 12 11 10 9 8
SUDPTRH
7 6 5 4 3 2 1 0
SUDPTRL
USBIE
T D
SUDPTRCTL
A
A=SDP Auto
A
USBIRQ
Interrupt Request:
T
Interrupt Control
D
A
T=Setup Token
D=Setup
Data
A=EP0 ACK
T=Setup Token
D=Setup Data
A=EP0 ACK
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