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High Performance Two Port 10/100 Managed Ethernet Switch with 32-Bit Non-PCI CPU Interface
Datasheet
Revision 1.4 (08-19-08) 108 SMSC LAN9312
DATASHEET
8.4.6 RX Data FIFO Direct PIO Reads
In this mode only A[2] is decoded, and any read of the LAN9312 will read the RX Data FIFO. This
mode is enabled when FIFO_SEL is driven high during a read access. This is normally accomplished
by connecting the FIFO_SEL signal to a high-order address line. This mode is useful when the host
processor must increment its address when accessing the LAN9312.
Timing is identical to a PIO read and the FIFO_SEL and END_SEL signals have the same timing
characteristics as the address lines. An RX Data FIFO direct PIO read cycle begins when both nCS
and nRD are asserted. Either or both of these control signals must de-assert between cycles for the
period specified in Table 15.10, “RX Data FIFO Direct PIO Read Cycle Timing Values,” on page 448.
The cycle ends when either or both nCS and nRD are de-asserted. These signals may be asserted
and de-asserted in any order. Read data is valid as indicated in the functional timing diagram in
Figure 8.5.
Note: A[9:3] are ignored during RX Data FIFO direct PIO reads.
Please refer to Section 15.5.6, "RX Data FIFO Direct PIO Read Cycle Timing," on page 448 for the
AC timing specifications for RX Data FIFO direct PIO read operations.
Figure 8.5 Functional Timing for RX Data FIFO Direct PIO Read Operation
VALID
D[31:0] (OUTPUT)
nCS, nRD
A[x:3]
VALID
END_SEL
VALID
A[2]
FIFO_SEL
(READ DATA FROM RX DATA FIFO)