COP884CG Datasheet, PDF (9/42 Pages) National Semiconductor (TI) – 8-Bit Microcontroller with UART and Three Multi-Function Timers

Reset (Continued)
TL DD 9765 – 10
RC l 5 c Power Supply Rise Time
FIGURE 5 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 6 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 input
Table B shows the variation in the oscillator frequencies as
functions of the component (R and C) values
TL DD 9765 – 12
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
5 6 100 1 1 to 1 3
6 8 100 0 9 to 1 1
Note 3k s R s 200k
50 pF s C s 200 pF
3 7 to 4 6
7 4 to 9 0
8 8 to 10 8
V_CC e 5V
V_CC e 5V
V_CC e 5V
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
T1C0
Timer T1 Start Stop control in timer
modes 1 and 2
Timer T1 Underflow Interrupt Pending Flag in
timer mode 3
T1C1
Timer T1 mode control bit
T1C2
Timer T1 mode control bit
T1C3
Timer T1 mode control bit
T1C3 T1C2 T1C1 T1C0 MSEL IEDG SL1 SL0
Bit 7
Bit 0
TL DD 9765–11
FIGURE 6 Crystal and R C Oscillator Diagrams
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