Manual

W78C438C
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AC CHARACTERISTICS
AC specifications are a function of the particular process used to manufacture the product, the ratings
of the I/O buffers, the capacitive load, and the internal routing capacitance. Most of the specifications
can be expressed in terms of multiple input clock periods (T
CP), and actual parts will usually
experience less than a ±20 nS variation.
Clock Input Waveform
PARAMETER SYMBOL MIN. TYP. MAX. UNIT NOTES
Operating Speed FOP 0 - 40 MHz 1
Clock Period TCP 25 - - nS 2
Clock High TCH 10 - - nS 3
Clock Low TCL 10 - - nS 3
Notes:
1. The clock may be stopped indefinitely in either state.
2. The T
CP specification is used as a reference in other specifications.
3. There are no duty cycle requirements on the XTAL1 input.
Program Fetch Cycle
PARAMETER SYMBOL MIN. TYP. MAX. UNIT
Address Valid to PSEN Low
T
APL 2 TCP --nS
PSEN Low to Data Valid
T
PDV --2 TCP nS
Data Memory Read/Write Cycle
PARAMETER SYMBOL MIN. TYP. MAX. UNIT
Address Valid to RD Low
T
ARL 4 TCP -
4 T
CP +∆
nS
RD Low to Data Valid
T
RDV --4 TCP nS
Data Hold After RD High
T
RDQ 0-2 TCP nS
RD Pulse Width
T
RS
6 TCP -∆
6 T
CP -nS
Address Valid to WR Low
T
AWL 4 TCP -
4 T
CP +∆
nS
Data Valid to WR Low
T
DWL 1 TCP --nS
Data Hold After WR High
T
WDQ 1 TCP --nS
WR Pulse Width
T
WS
6 TCP -∆
6 T
CP -nS
Note: "∆" (due to buffer driving delay and wire loading) is 20 nS.