Differences

This shows you the differences between two versions of the page.

--- cobo_clocking [2014/05/22 09:17] – abunimeh
+++ cobo_clocking [2014/05/23 14:18] (current) – [CKR and CKW] abunimeh
@@ Line 26: / Line 26: @@
 ===== CKR and CKW =====
-CKR and CKW are AGET chip Read and Write clocks. These clocks are passed from LMK04803B to an LVDS buffer on CoBo and sent over VHDCI cables to Asads. We have tested the communication with a 10 meter VHDCI cable with CKW running at 100MHz. The table below lists the trace lengths on the PCB. AS* are the signals from the LMK04803B to the LVDS buffer, CK* (shorter traces) are the signals from the LVDS buffer to the VHDCI connector.
+CKR and CKW are AGET chip Read and Write clocks. These clocks are passed from LMK04803B to an LVDS buffer on CoBo and sent over VHDCI cables to Asads. We have tested the communication with a 10 meter VHDCI cable with CKW running at 100MHz (For longer cables consider setting JP9 to 1-2). The table below lists the trace lengths on the PCB. AS* are the signals from the LMK04803B to the LVDS buffer, CK* (shorter traces) are the signals from the LVDS buffer to the VHDCI connector.
+{{ ::ck_buffers.png?500 |}}
 ^Name		^Node Count		^Routed (mil) ^^
@@ Line 67: / Line 69: @@
 ====== Synchronization ======
-To synchronize the LMK04803B clocks on a single CoBo board, one has to send a pulse (positive pulse, see datasheet for the minimum length of this pulse) from the FPGA to the LMK04803B chip using //PLL_SYNC// signal on pin F8. The length of the PCB trace is 1320.475 mils.
+To synchronize the LMK04803B clocks on a single CoBo board, one has to send a pulse (at least 0.5ns positive pulse, see datasheet for the minimum length of this pulse and polarity) from the FPGA to the LMK04803B chip using //PLL_SYNC// signal on pin F8. The length of the PCB trace is 1320.475 mils.
 The default configuration requires the Mutant and the CoBo to calibrate the GMC/WSCA links between them first. After that the Mutant sends a SYNC command to all CoBos on the WSCA line. CoBo uses that command to sync its own clocks.