COP888GD Datasheet, PDF (11/42 Pages) National Semiconductor (TI) – 8-Bit CMOS ROM Based Microcontrollers with 16k

Pin Descriptions
V_CC and GND are the power supply pins. All V_CC and GND
pins must be connected.
CKI is the clock input. This can come from an R/C generated
oscillator, or a crystal oscillator (in conjunction with CKO).
See Oscillator Description section.
RESET is the master reset input. See Reset Description sec-
tion.
The device contains three bidirectional 8-bit I/O ports (C, G
and L), where each individual bit may be independently con-
figured as an input (Schmitt Trigger inputs on ports L and G),
output or TRI-STATE under program control. Three data
memory address locations are allocated for each of these
I/O ports. Each I/O port has two associated 8-bit memory
mapped registers, the CONFIGURATION register and the
output DATA register. A memory mapped address is also re-
served for the input pins of each I/O port. (See the memory
map for the various addresses associated with the I/O ports.)
Figure 4 shows the I/O port configurations. The DATA and
CONFIGURATION registers allow for each port bit to be in-
dividually configured under software control as shown below:
CONFIGURATION
DATA
Port Set-Up
Register
Register
0
0
Hi-Z Input
(TRI-STATE Output)
0
1
Input with Weak Pull-Up
1
0
Push-Pull Zero Output
1
1
Push-Pull One Output
PORT L is an 8-bit I/O port. All L-pins have Schmitt triggers
on the inputs.
Port L supports Multi-Input Wake Up on all eight pins. L4 and
L5 are used for the timer input functions T2A and T2B. L6
and L7 are used for the timer input functions T3A and T3B.
Port L has the following alternate features:
L7 MIWU or T3B
L6 MIWU or T3A
L5 MIWU or T2B
L4 MIWU or T2A
L3 MIWU
L2 MIWU
L1 MIWU
L0 MIWU
Port G is an 8-bit port with 5 I/O pins (G0, G2–G5), an input
pin (G6), and a dedicated output pin (G7). Pins G0 and
G2–G6 all have Schmitt Triggers on their inputs. Pin G1
serves as the dedicated WDOUT WATCHDOG output, while
pin G7 is either input or output depending on the oscillator
mask option selected. With the crystal oscillator option se-
lected, G7 serves as the dedicated output pin for the CKO
clock output. With the single-pin R/C oscillator mask option
selected, G7 serves as a general purpose input pin but is
also used to bring the device out of HALT mode with a low to
high transition on G7. There are two registers associated
with the G Port, a data register and a configuration register.
Therefore, each of the 5 I/O bits (G0, G2–G5) can be indi-
vidually configured under software control.
Since G6 is an input only pin and G7 is the dedicated CKO
clock output pin (crystal clock option) or general purpose in-
put (R/C clock option), the associated bits in the data and
configuration registers for G6 and G7 are used for special
purpose functions as outlined on the next page. Reading the
G6 and G7 data bits will return zeros.
DS100076-5
FIGURE 4. I/O Port Configurations
Note that the chip will be placed in the HALT mode by writing
a “1” to bit 7 of the Port G Data Register. Similarly the chip
will be placed in the IDLE mode by writing a “1” to bit 6 of the
Port G Data Register.
Writing a “1” to bit 6 of the Port G Configuration Register en-
ables the MICROWIRE/PLUS to operate with the alternate
phase of the SK clock. The G7 configuration bit, if set high,
enables the clock start up delay after HALT when the R/C
clock configuration is used.
Config Reg.
Data Reg.
G7
CLKDLY
HALT
G6
Alternate SK
IDLE
Port G has the following alternate features:
G6 SI (MICROWIRE Serial Data Input)
G5 SK (MICROWIRE Serial Clock)
G4 SO (MICROWIRE Serial Data Output)
G3 T1A (Timer T1 I/O)
G2 T1B (Timer T1 Capture Input)
G0 INTR (External Interrupt Input)
Port G has the following dedicated functions:
G7 CKO Oscillator dedicated output or general purpose
input
G1 WDOUT WATCHDOG and/or Clock Monitor dedi-
cated output
Port C is an 8-bit I/O port. The 40-pin device does not have
a full complement of Port C pins. The unavailable pins are
not terminated. A read operation for these unterminated pins
will return unpredicatable values.
Port I is an 8-bit Hi-Z input port, and also provides the analog
inputs to the A/D converter. 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 from
these unterminated pins will return unpredictable values.
The user should ensure that the software takes this into ac-
count by either masking out these inputs, or else restricting
the accesses to bit operations only. If unterminated, Port I
pins will draw power only when addressed.
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