Motorola MC6805R Series Advance Information page 20

divided into two portions located from $080 to $OFF and $7CO to $F37. The portioning allows 128
bytes of ROM to be addressed with direct instructions. A RAM area of 64 bytes occupies $040 to
$07F. Only the 31 bytes from $061 to $07F can be used for the stack RAM due to the limitation im-
posed by the 5-bit stack pointer. The data direction, peripheral data, timer, and miscellaneous
registers are located from $000 to $OOF.
3.2 MC6805R2 MEMORY MAP
The memory map for the MC6805R2 is shown in Figure 3-2 and is identical to the MC6805U2 except
that two additional registers, the analog-to-digital control register and the analog-to-digital result
register, have been added at locations $OOE and $OOF, respectively.
Page Zero
Access with
Short
Instructions
Interrupt
Vectors
7
000
127
128
255
256
1983
1984
3895
3896
4087
4088
4089
4090
I-
4091
4092
I-
4093
4094
I-
4095
o
110 Ports
$000
Timer
RAM
(128 Bytes)
$07F
Page Zero
~-
User ROM
(128 Bytes)
$OFF
$100
Not Used
\
(1728 Bytes)
$7BF
$7CO
Main User
ROM
(1912 Bytes)
$F37
$F38
Self Check
ROM
(192 Bytes)
$FF7
$FF8
Timer Interrupt
$FF9
------
$FFA
External Interrupt
$FFB
- -
-
-
-
-
$FFC
SWI
$FFD
- -
- -
-
-
$FFE
RESET
$FFF
7 6 5 4 3 2 1 0
0
Port A Data Register
1
Port B Data Register
2
Port C Data Register
3
Port 0 Data Register
4
PortA DDR*
5
PortB DDR*
6
PortC DDR*
7
Not Used
8
Timer Data Register
9
Timer Control Register
10
Miscellaneous Register
11
Not Used
(3 Bytes)
13
14
AID Control Register
15
AID Result Register
16
Not Used
63
(48 Bytes)
64
RAM
(64 Bytes)
Stack
(31 Bytes
127
MaXt'um)
*Caution: Data direction registers (OORs) are write-only; they read as $FF.
Figure 3-2. MC6805R2 Memory Map
3-2
$000
$001
$002
$003
$004*
$005*
$006*
$007
$008
$009
$ooA
$ooB
$000
$ooE
$OOF
$010
$03F
$040
$07F