W78C438C Datasheet, PDF (12/16 Pages) Winbond – 8-BIT MICROCONTROLLER

W78C438C
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 (TCP), and actual parts will usually
experience less than a ±20 nS variation.
Clock Input Waveform
PARAMETER
Operating Speed
Clock Period
Clock High
Clock Low
SYMBOL
FOP
TCP
TCH
TCL
MIN.
0
25
10
10
Notes:
1. The clock may be stopped indefinitely in either state.
2. The TCP specification is used as a reference in other specifications.
3. There are no duty cycle requirements on the XTAL1 input.
TYP.
-
-
-
-
MAX.
40
-
-
-
UNIT
MHz
nS
nS
nS
NOTES
1
2
3
3
Program Fetch Cycle
PARAMETER
Address Valid to PSEN Low
PSEN Low to Data Valid
SYMBOL
TAPL
TPDV
MIN.
2 TCP
-
TYP.
-
-
MAX.
-
2 TCP
UNIT
nS
nS
Data Memory Read/Write Cycle
PARAMETER
Address Valid to RD Low
RD Low to Data Valid
Data Hold After RD High
RD Pulse Width
Address Valid to WR Low
Data Valid to WR Low
Data Hold After WR High
WR Pulse Width
SYMBOL
TARL
TRDV
TRDQ
TRS
TAWL
TDWL
TWDQ
TWS
MIN.
4 TCP
-
0
6 TCP -∆
4 TCP
1 TCP
1 TCP
6 TCP -∆
Note: "∆" (due to buffer driving delay and wire loading) is 20 nS.
TYP.
-
-
-
6 TCP
-
-
-
6 TCP
MAX.
4 TCP +∆
4 TCP
2 TCP
-
4 TCP +∆
-
-
-
UNIT
nS
nS
nS
nS
nS
nS
nS
nS
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