High Performance Two Port 10/100 Managed Ethernet Switch with 32-Bit Non-PCI CPU Interface
Datasheet
8.4.7RX Data FIFO Direct PIO Burst Reads
In this mode only A[2] is decoded, and any burst 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 burst read, and the FIFO_SEL and END_SEL signals have the same timing characteristics as the address lines.
In this mode, performance is improved by allowing an unlimited number of back-to-back DWORD read cycles. RX Data FIFO direct PIO burst reads can be performed using chip select (nCS) or read enable (nRD). An RX Data FIFO direct PIO burst read begins when both nCS and nRD are asserted. Either or both of these control signals must de-assert between bursts for the period specified in Table 15.11, “RX Data FIFO Direct PIO Burst Read Cycle Timing Values,” on page 449. The burst cycle ends when either or both nCS and nRD are de-asserted. They may be asserted and de-asserted in any order. Read data is valid as indicated in the functional timing diagram in Figure 8.6.
Note: Fresh data is supplied each time A[2] toggles.
Please refer to Section 15.5.7, "RX Data FIFO Direct PIO Burst Read Cycle Timing," on page 449 for the AC timing specifications for PIO RX Data FIFO direct PIO burst read operations.
FIFO_SEL
END_SEL
A[x:3]
A[2]
nCS, nRD
D[31:0] (OUTPUT)
(READ DATA FROM RX DATA FIFO)
Figure 8.6 Functional Timing for RX Data FIFO Direct PIO Burst Read Operation
SMSC LAN9312 | 109 | Revision 1.4 (08-19-08) |
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