CY7C68013
desired. Another bit within the IFCONFIG register will invert
the IFCLK signal whether internally or externally sourced.
3.13
External FIFO interface
3.13.1 Architecture
3.14
GPIF
The FX2 slave FIFO architecture has eight 512-byte blocks in
the endpoint RAM that directly serve as FIFO memories, and
are controlled by FIFO control signals (such as IFCLK, SLCS#,
SLRD, SLWR, SLOE, PKTEND, and flags).
The GPIF is a flexible 8- or 16-bit parallel interface driven by a
user-programmable finite state machine. It allows the
CY7C68013 to perform local bus mastering, and can
implement a wide variety of protocols such as ATA interface,
printer parallel port, and Utopia.
In operation, some of the eight RAM blocks fill or empty from
the SIE, while the others are connected to the I/O transfer
logic. The transfer logic takes two forms, the GPIF for internally
generated control signals, or the slave FIFO interface for
externally controlled transfers.
The GPIF has six programmable control outputs (CTL), nine
address outputs (GPIFADRx), and six general-purpose ready
inputs (RDY). The data bus width can be 8 or 16 bits. Each
GPIF vector defines the state of the control outputs, and deter-
mines what state a ready input (or multiple inputs) must be
before proceeding. The GPIF vector can be programmed to
advance a FIFO to the next data value, advance an address,
etc. A sequence of the GPIF vectors make up a single
waveform that will be executed to perform the desired data
move between the CY7C68013 and the external design.
3.13.2 Master/Slave Control Signals
The FX2 endpoint FIFOS are implemented as eight physically
distinct 256 x 16 RAM blocks. The 8051/SIE can switch any of
the RAM blocks between two domains, the USB (SIE) domain
and the 8051-I/O Unit domain. This switching is done virtually
instantaneously, giving essentially zero transfer time between
“USB FIFOS” and “Slave FIFOS.” Since they are physically the
same memory, no bytes are actually transferred between
buffers.
3.14.1 Six Control OUT Signals
The 100- and 128-pin packages bring out all six Control Output
pins (CTL0-CTL5). The 8051 programs the GPIF unit to define
the CTL waveforms. The 56-pin package brings out three of
these signals, CTL0–CTL2. CTLx waveform edges can be
programmed to make transitions as fast as once per clock
(20.8 ns using a 48-MHz clock).
At any given time, some RAM blocks are filling/emptying with
USB data under SIE control, while other RAM blocks are
available to the 8051 and/or the I/O control unit. The RAM
blocks operate as single-port in the USB domain, and dual-
port in the 8051-I/O domain. The blocks can be configured as
single, double, triple, or quad buffered as previously shown.
3.14.2 Six Ready IN Signals
The I/O control unit implements either an internal-master (M
for master) or external-master (S for Slave) interface.
The 100- and 128-pin packages bring out all six Ready inputs
(RDY0–RDY5). The 8051 programs the GPIF unit to test the
RDY pins for GPIF branching. The 56-pin package brings out
two of these signals, RDY0–1.
In Master (M) mode, the GPIF internally controls
FIFOADR[1..0] to select a FIFO. The RDY pins (two in the 56-
pin package, six in the 100-pin and 128-pin packages) can be
used as flag inputs from an external FIFO or other logic if
desired. The GPIF can be run from either an internally derived
clock or externally supplied clock (IFCLK), at a rate that
transfers data up to 96 Megabytes/s (48 MHz).
3.14.3 Nine GPIF Address OUT signals
Nine GPIF address lines are available in the 100- and 128-pin
packages, GPIFADR[8..0]. The GPIF address lines allow
indexing through up to a 512-byte block of RAM. If more
address lines are needed, I/O port pins can be used.
In Slave (S) mode, the FX2 accepts either an internally derived
clock or externally supplied clock (IFCLK, max. frequency 48
MHz) and SLCS#, SLRD, SLWR, SLOE, PKTEND signals
from external logic. Each endpoint can individually be selected
for byte or word operation by an internal configuration bit, and
a Slave FIFO Output Enable signal SLOE enables data of the
selected width. External logic must insure that the output
enable signal is inactive when writing data to a slave FIFO.
The slave interface can also operate asynchronously, where
the SLRD and SLWR signals act directly as strobes, rather
than a clock qualifier as in synchronous mode. The signals
SLRD, SLWR, SLOE and PKTEND are gated by the signal
SLCS#.
3.14.4 Long Transfer Mode
In master mode, the 8051 appropriately sets GPIF transaction
count registers (GPIFTCB3, GPIFTCB2, GPIFTCB1, or
GPIFTCB0) for unattended transfers of up to 4,294,967,296
bytes. The GPIF automatically throttles data flow to prevent
under or overflow until the full number of requested transac-
tions complete. The GPIF decrements the value in these
registers to represent the current status of the transaction.
3.15
USB Uploads and Downloads
The core has the ability to directly edit the data contents of the
internal 8-kbyte RAM and of the internal 512-byte scratch pad
RAM via a vendor-specific command. This capability is
normally used when “soft” downloading user code and is
available only to and from internal RAM, whether the 8051 is
held in reset or running. The available RAM spaces are 8
kbytes from 0x0000–0x1FFF (code/data) and 512 bytes from
0xE000–0xE1FF (scratch pad RAM).
3.13.3 GPIF and FIFO Clock Rates
An 8051 register bit selects one of two frequencies for the
internally supplied interface clock: 30 MHz and 48 MHz. Alter-
natively, an externally supplied clock of 5 MHz–48 MHz
feeding the IFCLK pin can be used as the interface clock.
IFCLK can be configured to function as an output clock when
the GPIF and FIFOs are internally clocked. An output enable
bit in the IFCONFIG register turns this clock output off, if
Note: A “loader” running in internal RAM can be used to
transfer downloaded data to external memory.
Document #: 38-08012 Rev. *E
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