• Utilizes the Tekmos 68HC24 Core
• Replaces ports B and C of 6811 type microprocessors.
• The chip-select function allows multiple TK68HC24s to be used in systems requiring multiple parallel ports.
• 3 – 5.5 Volt Operation.
• 0 – 5 MHz Operation.
• Supports all handshake and I/O modes.
• Available in 40 PDIP and 44 PLCC versions.

Ordering

The TK68HC24 can be ordered directly from Tekmos.

Volume production orders can be delivered within 12 weeks after the receipt of an accepted order. However, most orders are shipped on receipt.

Here is the pricing schedule for the TK68HC24.

Shipping

Domestic

Domestic shipping will be done as per customer preference.

International

The mail is the most cost effective method for international shipping of small quantities.  Depending on the country, the postage is between $5.00 to $12.00.

Courier service costs between $50.00 and $100, and is more appropriate for larger volumes.

Courier international shipments are to be made collect, for the purpose of billing the customs duties.

New Revision

The original wafer fab that makes the TK68HC24FN has been closed.  Tekmos has re-qualified the part on a new fab line.  The new part utilizes the same schematic as the old, and will meet the same specifications.  The new part started shipping in the first quarter of 2004.  Please contact us if you have any questions.

Design Details

This is a new part that has been designed to be identical in performance to the original part.  It is not the original part.  The only measurable difference we are aware of is that we deliberately added Schmitt triggers to all inputs.  The parts still meet the original DC and AC specifications.  But since it is being built in a newer, 0.8u technology, we were concerned that slower rise-times which worked on the original parts might cause problems in the newer technology.  The addition of a Schmitt trigger prevents that from being a problem.

There is one issue that some customers have faced.  The specification for input rise time is 20 ns.  However, some customers are using a RC circuit on the reset input that produces substantially longer rise times.  This problem may be aggravated when the reset signal goes off board, adding to the capacitance.

Parameters vary from lot to lot.  But generally, the input threshold for reset on the TK68HC24 is higher than both the original Freescale 68HC24 and that on the 68HC11 microprocessor.

If this is the case, and If reset has a slow rise time, then the 68HC11 processor can become active while the TK68HC24 is still in reset.  We have seen a case where the processor wrote initialization data to the TK68HC24 while it was still in reset, which caused a system failure.

The best fix is to not violate the input rise time specification.  A second fix is to install a software delay during initialization to allow reset to become a valid one level before writing to (or reading from) the TK68HC24.

Technical Assistance

Please send technical inquiries to This e-mail address is being protected from spam bots, you need JavaScript enabled to view it .  You can call as well, but a written question gives us the opportunity to provide a more detailed answer.