Connecting to your Target System – Chip Select
Many DDR333 systems qualify Command activity using the Chip Select lines, S0:3. This is either because they utilize “2T Timing” in whichheirt control lines (RAS, CAS, WE) may not fully transition to a valid state within one command clock, or because NOP commands are indicated only by releasing all chip selects rather than issuing an actual NOP command. Either of these conditions will make it difficult for the FS2331 to decode Commands properly without valid Chip Select signals.
Because Chip Select (S0:3) signals are routed independently to each DIMM slot and the FS2331 consumes a slot, the probe will not normally be able to see which memory a given command is directed to. As a result the probe cannot properly decode activity on DIMMs that is qualified by these signals unless they are brought to the probe. On some systems this will be seen as small or missing Data eyes after running Eyefinder . This problem can be corrected if the chip select signals for all memory ranks to be traced are made visible to the probe. The FS2331 user has several means for connecting up to 4 different Chip Select signals to the FS2331.
Chip Select Jumpers
The factory configuration of the FS2331 is a single jumper on J8 between pins 1 and 2. This forces S0 low (active) on the FS2331 and effectively qualifies ANY Command seen by the FS2331. This may be sufficient for the proper operation in your target system. If it is not, then there are 3 ways to bring active Chip Select signals to the FS2331. Please note that each of these methods requires all jumpers to be removed from J8.
1) Wiring Chip Select from a DIMM module to the FS2331
Four test points are provided on the DDR probe to allow you to probe Chip Selects from other DIMM slots on the target. You must solder a wire from the DIMM module and connect the wire to the appropriate test point on the FS2331. A table showing jumper configurations is provided. GND points are on J8 pins 2, 4, 6, and 8 to allow the use of twisted pairs . You should keep the wires as short as possible.
|
|
| If User is dedicating a | |
Chip Select line | Remove jumper | Connect wire from | DIMM slot, or using an | |
(factory config) | another DIMM to | Interposer (FS1024 or | ||
| ||||
|
|
| 1025) add | |
|
|
|
| |
S0 | J8 pins 1 and 2 | J5 pin 2 | Jumper J5 pins 1 and 2 | |
|
|
|
| |
S1 |
| J5 pin 4 | Jumper J5 pins 3 and 4 | |
|
|
|
| |
S2 |
| J5 pin 6 | Jumper J5 pins 5 and 6 | |
|
|
|
| |
S3 |
| J5 pin 8 | Jumper J5 pins 7 and 8 | |
|
|
|
| |
AnyCS (special) |
| J5 pin 10 | Jumper J5 pins 9 and 10 | |
|
|
|
|
20
