COP688CL Datasheet, PDF (13/40 Pages) National Semiconductor (TI) – General Description

Reset (Continued)
TL DD 9766 – 7
RC l 5 c Power Supply Rise Time
FIGURE 4 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 (1 t_c)
Figure 5 shows the Crystal and R C diagrams
CRYSTAL OSCILLATOR
CKI and CKO can be connected to make a closed loop
crystal (or resonator) controlled oscillator
Table A 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 avail-
able as a general purpose input and or HALT restart pin
Table B shows the variation in the oscillator frequencies as
functions of the component (R and C) values
TABLE A Crystal Oscillator Configuration T_A e 25 C
R1 R2 C1
C2
CKI Freq _Conditions
(kX) (MX) (pF) (pF)
(MHz)
0
1 30 30 – 36
10
V_CC e 5V
0
1 30 30 – 36
4
V_CC e 5 0V
0
1 200 100 – 150 0 455 V_CC e 5V
TABLE B RC Oscillator Configuration T_A e 25 C
R
C CKI Freq Instr Cycle
Conditions
(kX) (pF) (MHz)
(ms)
3 3 82 2 2 to 2 7 3 7 to 4 6
5 6 100 1 1 to 1 3 7 4 to 9 0
6 8 100 0 9 to 1 1 8 8 to 10 8
V_CC e 5V
V_CC e 5V
V_CC e 5V
Note 3k s R s 200k 50 pF s C s 200 pF
Control Registers
CNTRL Register (Address X 00EE)
The Timer1 (T1) and MICROWIRE PLUS control register
contains the following bits
SL1 SL0 Select the MICROWIRE PLUS clock divide
by (00 e 2 01 e 4 1x e 8)
IEDG
External interrupt edge polarity select
(0 e Rising edge 1 e Falling edge)
MSEL
Selects G5 and G4 as MICROWIRE PLUS
signals SK and SO respectively
TL DD 9766 – 9
TL DD 9766–8
FIGURE 5 Crystal and R C Oscillator Diagrams
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