COP87L88FH Datasheet, PDF (11/45 Pages) National Semiconductor (TI) – 8-Bit CMOS OTP Microcontrollers with 16k Memory,

Reset (Continued)
EXTERNAL OSCILLATOR
CKI can be driven by an external clock signal. CKO is avail-
able as a general purpose input and/or HALT restart control.
Crystal Oscillator
RC > 5 x Power Supply Rise Time
DS101135-8
FIGURE 6. Recommended Reset Circuit
Oscillator Circuits
The chip can be driven by a clock input on the CKI input pin
which can be between DC and 10 MHz. The CKO output
clock is on pin G7 (crystal configuration). The CKI input fre-
quency is divided down by 10 to produce the instruction
cycle clock (t_c).
Figure 7 shows the Crystal and R/C oscillator diagrams.
CRYSTAL OSCILLATOR
CKI and CKO can be connected to make a closed loop crys-
tal (or resonator) controlled oscillator.
Table 1 shows the component values required for various
standard crystal values.
R/C OSCILLATOR
By selecting CKI as a single pin oscillator input, a single pin
R/C oscillator circuit can be connected to it. CKO is available
as a general purpose input, and/or HALT restart input.
Table 2 shows the variation in the oscillator frequencies as
functions of the component (R and C) values.
DS101135-9
External Oscillator
DS101135-10
R/C Oscillator
DS101135-11
FIGURE 7. Crystal R/C, and
External Oscillator Diagrams
TABLE 1. Crystal Oscillator Configuration, T_A = 25˚C
R1 R2 C1 C2
(kΩ) (MΩ) (pF) (pF)
CKI Freq
Conditions
(MHz)
0
1 30 30–36
10
V_CC = 5V
0
1 30 30–36
4
V_CC = 5V
0
1 200 100–150 0.455
V_CC = 5V
TABLE 2. RC Oscillator Configuration, T_A = 25˚C
R
C
(kΩ) (pF)
3.3 82
5.6 100
6.8 100
CKI Freq
(MHz)
2.2 to 2.7
1.1 to 1.3
0.9 to 1.1
Instr. Cycle
(µs)
3.7 to 4.6
7.4 to 9.0
8.8 to 10.8
Conditions
V_CC = 5V
V_CC = 5V
V_CC = 5V
Note: 3k ≤ R ≤ 200k
50 pF ≤ C ≤ 200 pF
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