MC68HC711xxxx Motorola, MC68HC711xxxx Datasheet - Page 27

• Manufacturer Part Number: MC68HC711xxxx
• Description: Microcontrollers
• Manufacturer: Motorola

1.4.7.1 V
1.4.8 STRA/AS
1.4.9 STRB/R/W
M68HC11E Family — Rev. 5
MOTOROLA
RL
and V
RH
The V
When the voltage on this pin is more than one MOS threshold (about 0.7 volts)
above the V
from this signal rather than the V
without V
removed and must remain low until V
These two inputs provide the reference voltages for the analog-to-digital (A/D)
converter circuitry:
For proper A/D converter operation:
The strobe A (STRA) and address strobe (AS) pin performs either of two separate
functions, depending on the operating mode:
AS can be used to demultiplex the address and data signals at port C. Refer to
Section 2. Operating Modes and On-Chip
The strobe B (STRB) and read/write (R/W) pin act as either an output strobe or as
a data bus direction indicator, depending on the operating mode.
In single-chip operating mode, STRB acts as a programmable strobe for
handshake with other parallel devices. Refer to
(I/O) Ports
In expanded multiplexed operating mode, R/W is used to indicate the direction of
transfers on the external data bus. A low on the R/W pin indicates data is being
written to the external data bus. A high on this pin indicates that a read cycle is in
progress. R/W stays low during consecutive data bus write cycles, such as a
double-byte store. It is possible for data to be driven out of port C, if internal read
visibility (IRV) is enabled and an internal address is read, even though R/W is in a
high-impedance state. Refer to
Memory
•
•
•
•
•
•
STBY
V
V
V
V
In single-chip mode, STRA performs an input handshake (strobe input)
function.
In the expanded multiplexed mode, AS provides an address strobe function.
RL
RH
RH
RL
DD
for more information about IRVNE (internal read visibility not E).
is the low reference, typically 0 Vdc.
and V
pin is used to input random-access memory (RAM) standby power.
is the high reference.
should be at least 3 Vdc greater than V
for further information.
DD
power applied to the MCU. Reset must be driven low before V
voltage, the internal RAM and part of the reset logic are powered
RH
should be between V
General Description
Section 2. Operating Modes and On-Chip
DD
input. This allows RAM contents to be retained
DD
has been restored to a valid level.
SS
and V
Memory.
Section 6. Parallel Input/Output
DD
RL
.
.
General Description
Pin Descriptions
Data Sheet
DD
is
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