IA6805E2
29 August 2007
Microprocessor Unit
As of Production Version 00
Functional Description
Memory:
The MPU is capable of addressing 8192 bytes of memory and I/O registers. The locations
are divided into internal memory space and external memory space as shown in Figure 5.
The first 128 bytes of memory contain internal port I/O locations, timer locations, and 112
bytes of RAM. The MPU can read from or write to any of these locations. During program
reads from on chip locations, the MPU accepts data only from the addressed on chip
location. Any read data appearing on the input bus is ignored. The shared stack area is used
during interrupts or subroutine calls. A maximum of 64 bytes of RAM is available for stack
usage. The stack pointer is set to $7f at power up. The unused bytes of the stack can be used
for data storage or temporary work locations, but care must be taken to prevent it from
being overwritten due to stacking from an interrupt or subroutine call.
0
1
2
3
4
5
6
0
$0000
PORT A DATA REGISTER
PORT B DATA REGISTER
I/O PORTS
TIMER RAM
EXTERNAL MEMORY SPACE
EXTERNAL MEMORY SPACE
PORT A DATA DIRECTION REGISTER
PORT B DATA DIRECTION REGISTER
EXTERNAL MEMORY SPACE
EXTERNAL MEMORY SPACE
TIMER DATA REGISTER
127
128
$007F
$0080
ACCESS VIA
PAGE 0
DIRECT
ADDRESS
7
8
255
256
$00FF
$0100
9
TIMER CONTROL REGISTER
10
EXTERNAL MEMORY SPACE
15
16
EXTERNAL MEMORY
SPACE (8064 BYTES)
63
64
RAM
(112 BYTES)
TIMER INTERRUPT FROM WAIT STATE ONLY $1FF6 - $1FF7
TIMER INTERRUPT
EXTERNAL INTERRUPT
SWI
$1FF8 - $1FF9
$1FFA - $1FFB
$1FFC - $1FFD
$1FFE - $1FFF
INTERRUPT
VECTORS
STACK
(64 BYTES MAX)
8191
RESET
127
Figure 5. Memory Map
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IA211081401-03
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