SMSC LAN9312 - Manual (Page 107)

High Performance Two Port 10/100 Managed Ethernet Switch with 32-Bit Non-PCI CPU Interface
Datasheet
SMSC LAN9312 107 Revision 1.4 (08-19-08)
DATASHEET
8.4.5 PIO Burst Reads
In this mode, performance is improved by allowing up to 8 DWORD read cycles back-to-back. PIO
burst reads can be performed using Chip Select (nCS) or Read Enable (nRD). A 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 15.9, “PIO Burst Read Cycle Timing Values,” on
page 447 . 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 8.4 .
Note: Fresh data is supplied each time A[2] toggles.
The endian select signal (END_SEL) has the same timing characteristics as the upper address lines.
Please refer to Section 15.5.5, "PIO Burst Read Cycle Timing," on page 447 for the AC timing
specifications for PIO burst read operations.
Note: PIO burst reads are only supported for the RX Data FIFO. Burst reads from other registers are
not supported.
Figure 8.4 Functional Timing for PIO Burst Read Operation
END_SEL
A[x:5]
A[4:2]
nCS, nRD
D[31:0] (OUTPUT)
VALID
VALID VALID VALID VALID
VALID
VALID VALID VALID VALID