cop888eb National Semiconductor Corporation, cop888eb Datasheet - Page 14

• Manufacturer Part Number: cop888eb
• Description: 8-bit Cmos Rom Based Microcontrollers With 8k Memory, Can Interface, 8-bit A/d, And Usart
• Manufacturer: National Semiconductor Corporation

www.national.com
Functional Description
When using external reset, the external RC network shown
in Figure 6 should be used to ensure that the RESET pin is
held low until the power supply to the chip stabilizes. Under
no circumstances should the RESET pin be allowed to float.
RC
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. The CKI input frequency is divided by 10
to produce the instruction cycle clock (1/t
Figure 7 shows the Crystal diagram.
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.
Control Registers
CNTRL Register (Address X'00EE)
Bit 7
(k )
T1C3
TABLE 1. Crystal Oscillator Configuration, T
R1
0
0
0
>
5 x Power Supply Rise Time
(M )
FIGURE 6. Recommended Reset Circuit
T1C2
R2
FIGURE 7. Crystal Oscillator Diagram
1
1
1
(pF)
The RESET signal goes directly to the
HALT latch to restart a halted chip.
200
T1C1
C1
30
30
100–150
30–36
30–36
T1C0
(pF)
C2
DS012837-8
MSEL
CKI Freq.
(MHz)
0.455
10
4
(Continued)
IEDG
c
).
DS012837-7
Conditions
V
V
V
SL1
A
CC
CC
CC
= 25˚C
= 5V
= 5V
= 5V
SL0
Bit 0
14
Reserved
The Timer1 (T1) and MICROWIRE/PLUS control register
contains the following bits:
CNTRL Register (Address X'00EE)
The Timer1 (T1) and MICROWIRE/PLUS control register
contains the following bits:
PSW Register (Address X'00EF)
The PSW register contains the following select bits:
The Half-Carry flag is also affected by all the instructions that
affect the Carry flag. The SC (Set Carry) and R/C (Reset
Carry) instructions will respectively set or clear both the carry
flags. In addition to the SC and R/C instructions, ADC,
SUBC, RRC and RLC instructions affect the Carry and Half
Carry flags.
ICNTRL Register (Address X'00E8)
Bit 7
Bit 7
Bit 7
T1C3
HC
T1C3
T1C2
T1C1
T1C0
MSEL
IEDG
SL1 & SL0
T1C3
T1C2
T1C1
T1C0
MSEL
IEDG
SL1 & SL0
HC
C
T1PNDA Timer T1 Interrupt Pending Flag (Autoreload
T1ENA
EXPND
BUSY
EXEN
GIE
C
T1C2
LPEN
T1PNDA
Half Carry Flag
Carry Flag
RA in mode 1, T1 Underflow in Mode 2, T1A
capture edge in mode 3)
Timer T1 Interrupt Enable for Timer Underflow
or T1A Input capture edge
External interrupt pending
MICROWIRE/PLUS busy shifting flag
Enable external interrupt
Global interrupt enable (enables interrupts)
Timer T1 mode control bit
Timer T1 mode control bit
Timer T1 mode control bit
Timer T1 Start/Stop control in timer
modes 1 and 2, T1 Underflow Interrupt
Pending Flag in timer mode 3
Selects G5 and G4 as MICROWIRE/PLUS
signals SK and SO respectively
External interrupt edge polarity select
(0 = Rising edge, 1 = Falling edge)
Select the MICROWIRE/PLUS clock divide
by (00 = 2, 01 = 4, 1x = 8)
Timer T1 mode control bit
Timer T1 mode control bit
Timer T1 mode control bit
Timer T1 Start/Stop control in timer
modes 1 and 2, T1 Underflow Interrupt
Pending Flag in timer mode 3
Selects G5 and G4 as MICROWIRE/PLUS
signals SK and SO respectively
External interrupt edge polarity select
(0 = Rising edge, 1 = Falling edge)
Select the MICROWIRE/PLUS clock divide
by (00 = 2, 01 = 4, 1x = 8)
T0PND
T1C1
T1ENA
T0EN
T1C0
EXPND
µWPND
MSEL
µWEN
BUSY
IEDG
T1PNDB
EXEN
SL1
T1ENB
Bit 0
GIE
Bit 0
SL0
Bit 0