COP688CL Datasheet, PDF (11/40 Pages) National Semiconductor (TI) – General Description

AC Electrical Characteristics (Continued)
TL DD 9766 – 26
FIGURE 2 MICROWIRE PLUS Timing
Pin Descriptions
V_CC and GND are the power supply pins
CKI is the clock input This can come from an R C generat-
ed oscillator or a crystal oscillator (in conjunction with
CKO) See Oscillator Description section
RESET is the master reset input See Reset Description
section
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 G and L)
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
reserved for the input pins of each I O port (See the memo-
ry map for the various addresses associated with the I O
ports ) Figure 3 shows the I O port configurations The
DATA and CONFIGURATION registers allow for each port
bit to be individually configured under software control as
shown below
CONFIGURATION DATA
Register
Register
Port Set-Up
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 Wakeup (MIWU) on all eight
pins L4 and L5 are used for the timer input functions T2A
and T2B
Port L has the following alternate features
L0 MIWU
L1 MIWU
L2 MIWU
L3 MIWU
L4 MIWU or T2A
L5 MIWU or T2B
L6 MIWU
L7 MIWU
Port G is an 8-bit port with 5 I O pins (G0 G2 – G5) an input
pin (G6) and two dedicated output pins (G1 and 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 oscil-
lator mask option selected With the crystal oscillator option
selected 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 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 or general purpose input (R C clock config-
uration) the associated bits in the data and configuration
registers for G6 and G7 are used for special purpose func-
tions as outlined below Reading the G6 and G7 data bits
will return zeros
Note that the chip will be placed in the HALT mode by writ-
ing 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
enables the MICROWIRE PLUS to operate with the alter-
nate 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
G0 INTR (External Interrupt Input)
G2 T1B (Timer T1 Capture Input)
G3 T1A (Timer T1 I O)
G4 SO (MICROWIRE^TM Serial Data Output)
G5 SK (MICROWIRE Serial Clock)
G6 SI (MICROWIRE Serial Data Input)
TL DD 9766 – 6
FIGURE 3 I O Port Configurations
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