COP880C Datasheet, PDF (11/31 Pages) National Semiconductor (TI) – Microcontrollers

Typical Performance Characteristics (−40˚C ≤ T_A ≤ +85˚C) (Continued)
Port D Sink Current
Pin Descriptions
V_CC and GND are the power supply pins.
CKI is the clock input. This can come from an external
source, a R/C generated oscillator or a crystal (in conjunc-
tion with CKO). See Oscillator description.
RESET is the master reset input. See Reset description.
PORT I is an 8-bit Hi-Z input port. The 28-pin device does not
have a full complement of Port I pins. The unavailable pins
are not terminated i.e., they are floating. A read operation for
these unterminated pins will return unpredictable values.
The user must ensure that the software takes this into ac-
count by either masking or restricting the accesses to bit
operations. The unterminated Port I pins will draw power
only when addressed.
PORT L is an 8-bit I/O port.
PORT C is a 4-bit I/O port.
Three memory locations are allocated for the L, G and C
ports, one each for data register, configuration register and
the input pins. Reading bits 4–7 of the C-Configuration reg-
ister, data register, and input pins returns undefined data.
There are two registers associated with the L and C ports: a
data register and a configuration register. Therefore, each L
and C I/O bit can be individually configured under software
control as shown below:
Con- Data
Ports L and C Setup
fig.
0
0 Hi-Z Input (TRI-STATE Output)
0
1 Input with Pull-Up (Weak One Output)
1
0 Push-Pull Zero Output
1
1 Push-Pull One Output
On the 28-pin part, it is recommended that all bits of Port C
be configured as outputs.
PORT G is an 8-bit port with 6 I/O pins (G0–G5) and 2 input
pins (G6, G7). All eight G-pins have Schmitt Triggers on the
inputs.
There are two registers associated with the G port: a data
register and a configuration register. Therefore, each G port
bit can be individually configured under software control as
shown below:
DS010802-22
Con- Data
Port G Setup
fig.
0
0 Hi-Z Input (TRI-STATE Output)
0
1 Input with Pull-Up (Weak One Output)
1
0 Push-Pull Zero Output
1
1 Push-Pull One Output
Since G6 and G7 are input only pins, any attempt by the user
to configure them as outputs by writing a one to the configu-
ration register will be disregarded. Reading the G6 and G7
configuration bits will return zeros. The device will be placed
in the HALT mode by writing to the G7 bit in the G-port data
register.
Six pins of Port G have alternate features:
G0 INTR (an external interrupt)
G3 TIO (timer/counter input/output)
G4 SO (MICROWIRE serial data output)
G5 SK (MICROWIRE clock I/O)
G6 SI (MICROWIRE serial data input)
G7 CKO crystal oscillator output (selected by mask option)
or HALT restart input (general purpose input)
Pins G1 and G2 currently do not have any alternate func-
tions.
PORT D is an 8-bit output port that is preset high when
RESET goes low. Care must be exercised with the D2 pin
operation. At RESET, the external loads on this pin must
ensure that the output voltages stay above 0.9 V_CC to pre-
vent the chip from entering special modes. Also, keep the
external loading on D2 to less than 1000 pF.
Functional Description
Figure 1 shows the block diagram of the internal architec-
ture. Data paths are illustrated in simplified form to depict
how the various logic elements communicate with each
other in implementing the instruction set of the device.
ALU AND CPU REGISTERS
The ALU can do an 8-bit addition, subtraction, logical or shift
operation in one cycle time.
There are five CPU registers:
A is the 8-bit Accumulator register
PU is the upper 7 bits of the program counter (PC)
PL is the lower 8 bits of the program counter (PC)
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