Technical Data
MC68HC11E Family
—
Rev. 4
38
Pin Descriptions
MOTOROLA
Pin Descriptions
2.10 V
RL
and V
RH
These two inputs provide the reference voltages for the analog-to-digital
(A/D) converter circuitry:
V
RL
is the low reference, typically 0 Vdc.
V
RH
is the high reference.
For proper A/D converter operation:
V
RH
should be at least 3 Vdc greater than V
RL
.
V
RL
and V
RH
should be between V
SS
and V
DD
.
2.11 STRA/AS
The strobe A (STRA) and address strobe (AS) pin performs either of two
separate functions, depending on the operating mode:
In single-chip mode, STRA performs an input handshake (strobe
input) function.
In the expanded multiplexed mode, AS provides an address
strobe function.
AS can be used to demultiplex the address and data signals at port C.
Refer to
Section 4. Operating Modes and On-Chip Memory
.
2.12 STRB/R/W
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
Section 6. Parallel
Input/Output (I/O) Ports
for further information.
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