We are currently working with a custom board with four TigerSHARC processors (ADSP-TS201S) on it arranged in multiprocessor cluster configuration and connected in a single JTAG chain. On the board we have a switch that allows us to choose how to boot TigerSHARC processors - from EPROM or to idle and wait for an external device to boot DSPs. In idle after reset mode we can successfully connect through JTAG to all processors and work with them (halt, watch and edit registers and memory, download program etc.), although sometimes when disconnecting from target we have messages about some JTAG register scan failures. In boot from EPROM mode even when an EPROM is fully erased sometimes we cannot connect through JTAG to the processors - connect to target fails, or we can connect but cannot work with DSPs - we cannot even halt them, such tries fail with messages like "JTAG scan failed..." and "Emulator HW could't scan EMUCTL or EMUPC register". In both cases ICE Test reports no problem. That issue exists only on one board, all the others work fine. Could you suggest something that can help us to figure out what's going wrong here?!
And one more thing. In VisualDSP there is a menu that allows to select JTAG Frequency but it allows to do so only if the session is already started and all processors are halted. Is there any way to somehow override default JTAG frequency when connecting to target?! We use ADZS-USB-ICE and see on oscilloscope that connection with target is established at frequency of 10 MHz. Is there way to lower the frequency to 5 MHz?!
Thanks in advance,