MC68336/376
ELECTRICAL CHARACTERISTICS
MOTOROLA
USER’S MANUAL
Rev. 15 Oct 2000
A-8
Figure A-1 CLKOUT Output Timing Diagram
Figure A-2 External Clock Input Timing Diagram
6. Specification 9A is the worst-case skew between AS and DS or CS. The amount of skew depends on the relative
loading of these signals. When loads are kept within specified limits, skew will not cause AS and DS to fall outside
the limits shown in specification 9.
7. If multiple chip selects are used, CS width negated (specification 15) applies to the time from the negation of a
heavily loaded chip select to the assertion of a lightly loaded chip select. The CS width negated specification
between multiple chip selects does not apply to chip selects being used for synchronous ECLK cycles.
8. Hold times are specified with respect to DS or CS on asynchronous reads and with respect to CLKOUT on fast
cycle reads. The user is free to use either hold time.
9. Maximum value is equal to (tcyc / 2) + 25 ns.
10. If the asynchronous setup time (specification 47A) requirements are satisfied, the DSACK[1:0] low to data setup
time (specification 31) and DSACK[1:0] low to BERR low setup time (specification 48) can be ignored. The data
must only satisfy the data-in to clock low setup time (specification 27) for the following clock cycle. BERR must
satisfy only the late BERR low to clock low setup time (specification 27A) for the following clock cycle.
11. To ensure coherency during every operand transfer, BG will not be asserted in response to BR until after all cycles
of the current operand transfer are complete and RMC is negated.
12. In the absence of DSACK[1:0], BERR is an asynchronous input using the asynchronous setup time (specification
47A).
13. After external RESET negation is detected, a short transition period (approximately 2 tcyc) elapses, then the SIM
drives RESET low for 512 tcyc.
14. External assertion of the RESET input can overlap internally-generated resets. To insure that an external
reset is recognized in all cases, RESET must be asserted for at least 590 CLKOUT cycles.
15. External logic must pull RESET high during this period in order for normal MCU operation to begin.
68300 CLKOUT TIM
4
CLKOUT
5
2
3
1
68300 EXT CLK INPUT T
4B
EXTAL
5B
2B
3B
1B
NOTE: TIMING SHOWN WITH RESPECT TO 20% AND 70% VDD.
PULSE WIDTH SHOWN WITH RESPECT TO 50% VDD.