ATDH1165PC- Atmel, ATDH1165PC- Datasheet - Page 40

• Manufacturer Part Number: ATDH1165PC-
• Manufacturer: Atmel

Specifications of ATDH1165PC-

• Lead Free Status / Rohs Status: Not Compliant

Atmel ATF15xx Family: ISP Devices User Guide
12. During ISP programming, all I/O pins are in one of the following conditions:
13. Don’t use multiple JTAG chains on one board.
14. Avoid long (+5 devices) JTAG devices chains.
15. Buffer all JTAG pins directly at the header.
16. Use a slower TCK frequency.
17. Terminate JTAG signals at header.
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High-impedance state:
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Weakly latched to the previous state:
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Devices may interact between different JTAG chains.
Board is functional only when all devices in all JTAG chains are programmed
successfully.
If programming fails for at least one device in a chain while other JTAG chains
were successfully programmed:
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Solution: Use one JTAG chain to link all devices on the board.
If you must generate a long chain, buffer the TMS, TCK signal between devices.
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Buffers reshape rise times on TMS and TCK signals.
Alternate approach to handling long JTAG chains
Assures clean rising edges on all JTAG signals
TCK skew may cause setup/hold violations on long device chains for faster
clock frequencies.
Slower frequency signals are less subject to transmission line effects (ringing,
overshoot), which can cause programming problems.
Slower signal frequency generates less noise/crosstalk on cable.
Both active and passive termination are acceptable. However, passive termina-
tion is preferred.
Reduces ringing due to long cable/PCB trace lengths.
Termination is most critical for TMS and TCK.
When a blank/erased device is programmed
When a device is reprogrammed with the pin-keeper circuits disabled
Prevents bus contention with external devices interfacing with Atmel device
on the circuit board
When a programmed device is reprogrammed with the pin-keeper circuits
enabled
I/O pins keep previous logic levels, prior to ISP
Prevents ISP from affecting the operation of other devices on the system
board
Either Atmel or other devices on board can be damaged.
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System board operational state is undefined.
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Schmitt trigger buffers preferred
Possible bus contention problem for tri-stateable outputs
Incorrect functional operation may occur
JTAG ISP Guidelines
6-3