15
SS: KEYPAD
The SS: KEYPAD connector is an ten pin connector that implements 4 bits of Port D and 4
bits of Port E as a simple serial or keypad interface. This interface provides connection to
the SPI port on Port D as a simple serial interface or may be implemented as a software key
scan for a passive keypad.
This board is manufactured with no connectors installed in pins 1 and 2. This is to prevent
confusion when connecting an 8-pin keypad. Pins 1 and 2 are available however for SPI
port applications. When connecting the keypad, align the RED stripe closest to pin 1.
Example programs using this keypad are provided on the CD. See the files:
KLCD-E.C
KEYLCD-E.C
KEYLCD-E.ASM
1 2 3 4 5 6 7 8 9 10
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+5 Gnd D2 D3 D4 D5 E0 E1 E2 E3
MCU_PORT
The 68HC11E9 is configured for expanded / multiplexed mode. It uses Port B and Port C for
address and data buss to external memory and memory mapped I/O devices. This leaves
CPU Port D, Port A, and Port E to provide all other parallel I/O from the controller. MCU port
lines are mixed as input only, output only, and some are input or output. All MCU port lines
serve dual functions with internal CPU peripherals such as the timer subsystem and port A,
the A/D converter on port E, and the SPI or SCI on port D.
PD0/RXD0
1
2
PD1/TXD0
PD2/SI
3
4
PD3/SO
PD4/SCLK
5
6
PD5/SEL0
PA0
7
8
PA1
PA2
9
10
PA3
PA4
11
12
PA5
PA6
13
14
PA7
PE7
15
16
PE3
PE6
17
18
PE2
PE5
19
20
PE1
PE4
21
22
PE0
VRL
23
24
VRH
The MCU_PORT connector is a dual row 13 pin Berg-
style connector ( 26 pins total ) which is configured as
shown.
PD0 and PD1 are used by the SCI to implement COM1.
PD<2:5> are used by the HC11 SPI to implement the SS:
KEYPAD port. These port D lines can also be used for
parallel I/O, but then they will not be available for COM1
or the SS: KEYPAD port. Use caution when assigning
port D lines to functions other than COM1 and the SS:
KEYPAD port.
Gnd.
25
26
+5V
A/D REFERENCE
The VRH and VRL lines from the HC11 are connected to +5v through R3 and to ground
through R2 respectively. These two resistors are located next to the MCU_PORT header.
The resistors are identified on the silk screen by their reference designators. The
appropriate resistor(s) need to be removed in order to apply an external reference to the
VRH and/or VRL inputs.
