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What is the maximum crystal frequency which I can use on hc11 E family? I can not find it on the data sheet. Thank you

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The 'bus freq' is either 2,3,4 or 5 MHz on diff flavors. Thats xtal freq of 8,12,16,20 MHz [Non-text portions of this message have been removed]

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Normally either 8 or 12 MHz depending on the part that you buy. -2 parts are 2 mHZ bus speeds (8 Mhz crystal), -3 parts are 3 MHz bus speed. See the E series Technical Data Sheet for the electrical specifications. Note, the -2 parts are becomming hard to shop because most vendors stock the -3 parts. Bob Smith --- Avoid computer viruses, Practice safe hex --- -- Specializing in small, cost effective embedded control systems -- http://www.smithmachineworks.com/embedprod.html Robert L. (Bob) Smith Smith Machine Works, Inc. 9900 Lumlay Road Richmond, VA 23236 804/745-2608 ----- Original Message ----- From: "aporaria" <> To: <> Sent: Thursday, April 29, 2004 3:58 PM Subject: [m68HC11] Cyrstal on m68hc11E > What is the maximum crystal frequency which I can use on hc11 E > family? I can not find it on the data sheet. > Thank you > > -------------------------------------------------------------------------- ------ > Yahoo! Groups Links > > a.. To

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--- In , "aporaria" <afshin@p...> wrote: > What is the maximum crystal frequency which I can use on hc11 E > family? I can not find it on the data sheet. Look at the part number printed on the HC11 device you are using. The very last digit of the part number (usually) specifies the 'speed grade' of the device. This number will be either 2, 3, 4 or 5. Multiply this number b 4 MHz to determine the maximum crystal/clock frequency you can use with the device. For example, if the part you have has the following part number stamped on it: MC68HC711E9CFN2 The very last digit - '2' in this case - indicates that this device can accept a maximum clock of 2 x 4 MHz = 8 MHz. Note that I have seen some HC11's - like older E2 'XC'-prefix parts - that do not have the speed-grade suffix in their part number. If this is the case with your device, then you should assume that the speed grade is '2' (8 MHz xtal). FYI, the reason that the number used here is a '2' instead of a '8' is that this value indicates the maximum speed of the INTERNAL CPU clock, usually referred to as the 'E clock' in Motorola documentation, as this is the rate at which the bus-enable (E) output runs at when the device is configured for external bus operation. The external clock is divided by 4 by the HC11 clock generator subsystem before it is fed to the rest of the HC11 subsystems, including the CPU. If, for example, you are wondering how fast a given HC11 instruction will execute, and look up this information in the reference manual, you will find that the execution times are expressed in E-clock cycles. Thus, an instruction such as NOP, which takes 2 E-clocks to execute, will have a execution time of (2 / 2 MHz = 2 * 500 nS = 1 uS) if the external clock is running at 8 MHz.

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Thanks for all the replies. regards

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