Figure 8-1 Clock Synchronization - ARM ARM966E-S Technical Reference Manual

8.1.2 Clocks
ARM DDI 0186A
The system and test clocks must be synchronized externally to the ARM966E-S
macrocell. The ARM Multi-ICE debug agent directly supports one or more cores within
an ASIC design. To synchronize off-chip debug clocking with the ARM966E-S
macrocell requires a three-stage synchronizer. The off-chip device (for example,
Multi-ICE) issues a TCK signal, and waits for the RTCK (Returned TCK) signal to
come back. Synchronization is maintained because the off-chip device does not
progress to the next TCK until after RTCK is received.
Figure 8-1 shows this synchronization.
TDO
RTCK
TCK
D Q
CLK
TMS
TDI
Multi-ICE
interface
pads
Copyright © 2000 ARM Limited. All rights reserved.
D Q D Q
TCK Synchronizer
Debug Support
DBGnTRST
DBGTCKEN
D Q
CLK
D Q
CLK
Input sample and hold

Figure 8-1 Clock synchronization

DBGTDO
DBGTMS
DBGTDI
CLK
8-3