pc87591l-n05 National Semiconductor Corporation, pc87591l-n05 Datasheet - Page 235

• Manufacturer Part Number: pc87591l-n05
• Description: Lpc Mobile Embedded Controller
• Manufacturer: National Semiconductor Corporation

Revision 1.2
4.0 Embedded Controller Modules
4.19.8 Usage Hints
JTAG Performance
For best performance, the PC87591L-N05 should be the only device in the scan path. Since the Debugger interface is used
in the development phase of the product, this should not be a problem. Keep the scan path as short as possible.
JTAG Clock Rate
For reliable communication over the JTAG serial bus, the error probability should be extremely low. This can be achieved
by connecting the TAP to the JTAG bus controller card, paying attention to the TCK frequency, signal timing, this cable type
and cable length (for long cables, transceivers may be required).
Communication Lockout
Some erroneous operations by the host may cause a lockout of the communication hardware. Examples of such cases are:
A reset instruction is guaranteed to recover from all of these locked cases, but it resets the entire PC87591L-N05.
• Performing a data scan when the JTAG instruction is SCAN_RX with a PID value of ‘1111’
• Performing a data scan with a JTAG instruction with a PID value that is not in the system (i.e., PID > 0)
• Performing a SCAN_TX when the PID value is ‘1111’
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