80C251SB16 Datasheet, PDF (19/36 Pages) Intel Corporation – HIGH-PERFORMANCE CHMOS MICROCONTROLLER

8XC251SA/SB/SP/SQ HIGH-PERFORMANCE CHMOS MICROCONTROLLER
5.2 Definition of AC Symbols
Table 10. AC Timing Symbol Definitions
Signals
A Address
D Data In
L ALE
Q Data Out
R RD#/PSEN#
W WR#
Conditions
H High
L Low
V Valid
X No Longer Valid
Z Floating
5.3 A.C. Characteristics
Test Conditions: Capacitive load on all pins = 50 pF.
Table 11 lists AC timing parameters for the
8XC251SA/SB/SP/SQ with no wait states. External
wait states can be added by extending
PSEN#/RD#/WR# and/or by extending ALE. In the
table, Notes 3 and 5 mark parameters affected by an
ALE wait state, and Notes 4 and 5 mark parameters
affected by a PSEN#/RD#/WR# wait state.
Figures 8–10 show the bus cycles with the timing
parameters.
Table 11. AC Characteristics
Symbol
Parameter
@ Max F_osc (1)
Min Max
F_osc Variable
Min
Max
F_OSC
T_OSC
XTAL1 Frequency
1/F_OSC
@ 12 MHz
@ 16 MHz
N/A N/A
0
16
N/A N/A
83.3
62.5
T_LHLL
ALE Pulse Width
@ 12 MHz
@ 16 MHz
73.3
52.5
(1+2M)
T_OSC – 10
T_AVLL
Address Valid to ALE Low
@ 12 MHz
@ 16 MHz
58.3
37.5
(1+2M)
T_OSC – 25
T_LLAX
Address Hold after ALE Low
@ 12 MHz
15
@ 16 MHz
15
15
NOTES:
1. 16 MHz.
2. Specifications for PSEN# are identical to those for RD#.
3. In the formula, M=Number of wait states (0 or 1) for ALE.
4. In the formula, N=Number of wait states (0,1,2, or 3) for RD#/PSEN#/WR#.
5. “Typical” specifications are untested and not guaranteed.
Units
MHz
ns
ns
(3)
ns
(3)
ns
PRELIMINARY
19