Z86C61 Datasheet, PDF (19/46 Pages) Zilog, Inc. – CMOS Z8 MICROCONTROLLER

FUNCTIONAL DESCRIPTION
Z86C61/62/96
Z8^® MICROCONTROLLER
Address Space
Program Memory. The Z86C61/62 can address up to 48
Kbytes of external program memory (Figure 16). The first
12 bytes of program memory are reserved for the interrupt
vectors. These locations contain six 16-bit vectors that
correspond to the six available interrupts. For ROM mode,
byte 13 to byte 16383 consists of on-chip ROM. At ad-
dresses 16384 and greater, the Z86C61/62 executes
external program memory fetches. The Z86C96, and the
Z86C61/62 in ROMless mode, can address up to 64
Kbytes of external program memory. Program execution
begins at external location 000CH after a reset.
Data Memory (/DM). The ROM version can address up to
48 Kbytes of external data memory space beginning at
location 16384. The ROMless version can address up to 64
Kbytes of external data memory. External data memory
may be included with, or separated from, the external
program memory space. /DM, an optional I/O function that
can be programmed to appear on pin P34, is used to
distinguish between data and program memory space
(Figure 17). The state of the /DM signal is controlled by the
type instruction being executed. An LDC opcode refer-
ences PROGRAM (/DM inactive) memory, and an LDE
instruction references DATA (/DM active Low) memory.
65535
16384
16383
External
ROM and RAM
On-Chip ROM
65535
Location of ₁₂
First Byte of
Instruction ₁₁
Executed
After RESET ₁₀
9
8
Interrupt ⁷
Vector
(Lower Byte)
6
5
4
Interrupt
Vector
(Upper Byte)
3
2
1
0
IRQ5
IRQ5
IRQ4
IRQ4
IRQ3
IRQ3
IRQ2
IRQ2
IRQ1
IRQ1
IRQ0
IRQ0
External
Data
Memory
16384
16383
0
Not Addressable
Figure 17. Data Memory Configuration
Figure 16. Program Memory Configuration
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