Memory Variables

1
Memory Variables
file memtest.asm This program illustrates how
to latch input from switches, XOR and how to
store a value in memory. Illustrates 3 different
methods to access memory. D port for input, A
port for output For the 68HC11 MicroStamp11, Dr.
Hoganson, 12/04/02
definitions rbase eq
u 0000 beginning of register/memory port_a equ r
base0 port A is the first register port_d equ rb
ase8 port D is the input port note that
port_d 0 is RXD, 1 is TXD, so can't
use h_sec equ ffff delay loop value (about 1/2
second) memtest equ rbase100 location
to store variable memtest dat
a section
org 0100 mem2 rmb
1 note that memtest and mem2 are at the
same location in memory. Creates 1 byte. mem3
fcb 00 located at 0101, contents
00 code section
org e000 beginning of EEPROM
(68HC811E2) begin ldaa 04 value to disable
timed interrupt staa 3f disables an timed
interrupt lds ff set stack start ldaa 00
clear staa port_a loop ldab port_d pins 20
and 19 in use stab mem3 substitute mem2 or
memtest

• Three methods
• Equate label to a location
• Declare/reserve memory using rmb or fcb