Cypress Semiconductor FX2LP Información técnica Pagina 177

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Chapter 9. Slave FIFOs Page 9-21
Figure 9-26. EPx Memories
9.3.3 Slave FIFO Programmable-Level Flag (PF)
Each FIFO’s programmable-level flag (PF) asserts when the FIFO reaches a user-defined fullness
threshold. That threshold is configured as follows:
1. For OUT packets: The threshold is stored in PFC12:0. The PF is asserted when the number of
bytes in the entire FIFO is less than/equal to (DECIS=0) or greater than/equal to (DECIS=1)
the threshold.
2. For IN packets, with PKTSTAT = 1: The threshold is stored in PFC9:0. The PF is asserted
when the number of bytes written into the current packet in the FIFO is less than/equal to
(DECIS=0) or greater than/equal to (DECIS=1) the threshold.
3. For IN packets, with PKTSTAT = 0: The threshold is stored in two parts: PKTS2:0 holds the
number of committed packets, and PFC9:0 holds the number of bytes in the current packet.
The PF is asserted when the FIFO is at or less full than (DECIS=0), or at or more full than
(DECIS=1), the threshold.
By default, FLAGA is the Programmable-Level Flag (PF) for the endpoint currently pointed to by
the FIFOADR[1:0] pins. For EP2 and EP4, the default endpoint configuration is BULK, OUT, 512,
2x, and the PF pin asserts when the entire FIFO has greater than/equal to 512 bytes. For EP6 and
EP8, the default endpoint configuration is BULK, IN, 512, 2x, and the PF pin asserts when the
entire FIFO has less than/equal to 512 bytes.
In other words, the default-configuration PFs for EP2 and EP4 assert when the FIFOs are half-full,
and the default-configuration PFs for EP6 and EP8 assert when those FIFOs are half-empty.
See Chapter 15, "Registers," for full details.
FLAGA
FIFOADR[1:0]
Slave FIFOs 8051 Registers Device Pins
FLAGB
FLAGC
FLAGD/SLCS#
SLOE
SLRD
SLWR
PKTEND
FD[15:0]
EP4FIFOBUF
EP6FIFOBUF
EP8FIFOBUF
EP2FIFOBUF
EP8
EP6
EP4
EP2
IFCLK
30/48MHz
5 - 48MHz
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