SMSC LAN9311i - Manual (Page 108)

Two Port 10/100 Managed Ethernet Switch with 16-Bit Non-PCI CPU Interface
Datasheet
Revision 1.4 (08-19-08) 108 SMSC LAN9311/LAN9311i
DATASHEET
8.5.5 PIO Burst Reads
In this mode, performance is improved by allowing up to 16 WORD 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 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 8.4 .
Note: A[1] must toggle during burst reads. Fresh data is supplied each time A[1] is toggled.
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 449 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[4:1]
nCS, nRD
D[15:0] (OUTPUT)
VALID
VALID VALID VALID VALID
VALID
VALID VALID VALID VALID