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
. 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
.
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
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