Parallel Ports, SS Keboard | Motorola CMD11E1 guide

SS: KEBOARD

The SS:KEYBOARD interface is available but not brought out to a connector. It can be implemented with software drivers through the SPI feature of the 68HC11. Such a configuration is used with a serially encoded keyboard. This port can also be used as a keypad by using PD<2:5> as column lines with E<1:4> as row lines. Note that E<1:4> are open termination’s with pull-down resistors on the board. E<1:4> are ONLY connected to pins 7, 8, 9, and 10 of the SS:KEYBOARD connector. In order to use those pins, E<1:4> must be connected to I/O lines. AUX_PORT C is recommended because it is capable of nibble or 4 bit configuration. While such a dual parallel matrix will work, it dedicates the SPI to keypad use only. If implemented through the SPI as a SIMPLE SERIAL port, four separate, additional SPI serial devices can be supported by the SEL lines defining E<1:4> for a total of five slave serial devices. (Note: this still requires E<1:4> be connected. Each to its own I/O line, but this will support four additional peripheral devices.)

1	¨	+5
2	¡	GND
3	¡	PD2/SI
4	¡	PD3/SO	SPI
5	¡	PD4/SCLK	SPI
5	¡	PD4/SCLK
6	¡	PD5/SEL0
7	¡	SEL1		E1
8	¡	SEL2	Auxiliary select lines terminated to ground	E2
9	¡	SEL3	(10kohm)	E3
10	¡	SEL4		E4

See the files called KLCD-E.C,KEYLCD-E.C,KEYLCD-E.ASMon the support CD for example programs using this connector.

PARALLEL PORTS

The 68HC11 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. CPU port lines are mixed as input only, output only, and some are input or output. All CPU 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.

To increase general purpose input/output capability an 82C55 peripheral port expander is memory mapped onto the data buss providing three auxiliary ports. The auxiliary port lines are all input or output configurable and are available on the AUX_PORT connector. All port lines are limited to sinking and sourcing approximately 1mA. maximum. Refer to Chapter 6 Memory Map and Appendix C for more information on the 82C55.