Hardware and Software Design • Manufacturing Services
page 22
The Length register is the number of 64 bit words to transfer into or out of SDRAM. The number of words
transferred is N. The count operates from 1<->N providing the transfer length. Because we do not use “0” as a
length the address generator can reach 64M-1 [all but 1 64 bit word] words from any one channel in one
transfer. With a split transfer the full space can be filled, with multiple channels the full space can be reached. It
is intended that the Address Generator defined length control the transfer size. The FE Xilinx should be set to
continuous unless in XYZ mode.
Address Generator SDRAM Control Registers
00A0
ADD0_3
CNTL CH 0
00A4
ADD0_3
CNTL CH 1
00A8
ADD0_3
CNTL CH 2
00AC
ADD0_3
CNTL CH 3
01A0
ADD4_7
CNTL CH 4
01A4
ADD4_7
CNTL CH 5
01A8
ADD4_7
CNTL CH 6
01AC
ADD4_7
CNTL CH 7
Read – Write
Bit#
Definition
7
Start for Channel x
6-3
unused / undefined mask off for read-back
2
IO – set to 1 for write to SDRAM, 0 for Read
1
DIR – set to 0 for SDRAM capture/retrieve, 1 for Direct
0
Load – set to 0 for preload 1 for start with next address
Eight registers at different offsets; bit definitions provided for the 0..7 channels. The Cntl register starts the
transfer for a particular channel, controls whether to pre-load the address, and sets the mode of operation. In
multi-channel operation it is important that the active channels are programmed to the same mode. Channel 0
and Channel 4 must be used for retrieve mode. The starting address can be programmed to any location in
SDRAM. Only one channel can be read at a time [Retrieve]. Inadvertent retrieve commands to channel[s] 1,2,3