Designing Hardware for QuickUSB
GPIF Master Mode
In GPIF master mode, the QuickUSB module controls all aspects of the HSPP
and the host PC initiates all data transfers through the QuickUSB module. This
mode is implemented using the GPIF programmable DMA engine built into the
FX2. All GPIF master mode HSPP transfers are synchronous with IFCLK and are
controlled by CMD_DATA, REN, WEN and OE. CMD_DATA indicates whether the
HSPP transfer was initiated by the command or data functions. REN indicates
read a transfer and WEN indicates a write transfer. OE indicates a read
transfer prior to actually asserting the REN signal so that the peripheral can
prepare to execute a read transfer.
Command Transfers
Command transfers are low-speed transfers that use the data bus (FD) and the
address bus (GPIFADR) to read and write data to and from the target hardware.
The
functions are used
to perform command transfers. They transfer data one element at a time with
the CMD_DATA line set high (‘1’). Command transfers were designed to control
registers in a peripheral connected to the HSPP, but they can be used for any
type of bi-directional low speed parallel I/O.
Data Transfers
Data transfers are high-speed block-oriented data transfers that use the data
bus (FD) and the address bus (GPIFADR) to read and write data to either a FIFO
or a memory in the target hardware. The
and
functions are used to perform high-speed data transfers.
They transfer data in a burst of data blocks with the CMD_DATA line set low
(‘0’). A single call from QuickUsbReadData or QuickUsbWriteData will be broken
down into a series of data blocks transferred over the HSPP.
High Speed Parallel Port
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