IS89C51 Datasheet, PDF (7/48 Pages) Integrated Silicon Solution, Inc – CMOS SINGLE CHIP 8-BIT MICROCONTROLLER with 4-Kbytes of FLASH

IS89C51
ISSI ^®
OPERATING DESCRIPTION
The detail description of the IS89C51 included in this
description are:
• Memory Map and Registers
• Timer/Counters
• Serial Interface
• Interrupt System
• Other Information
• Flash Memory
MEMORY MAP AND REGISTERS
Memory
The IS89C51 has separate address spaces for program
and data memory. The program and data memory can be
up to 64K bytes long. The lower 4K program memory can
reside on-chip. Figure 5 shows a map of the IS89C51
program and data memory.
The IS89C51 has 128 bytes of on-chip RAM, plus numbers
of special function registers. The lower 128 bytes can be
accessed either by direct addressing or by indirect
addressing. Figure 6 shows internal data memory
organization and SFR Memory Map.
The lower 128 bytes of RAM can be divided into three
segments as listed below and shown in Figure 7.
1. Register Banks 0-3: locations 00H through 1FH (32
bytes). The device after reset defaults to register bank
0. To use the other register banks, the user must select
them in software. Each register bank contains eight 1-
byte registers R0-R7. Reset initializes the stack point
to location 07H, and is incremented once to start from
08H, which is the first register of the second register
bank.
2. Bit Addressable Area: 16 bytes have been assigned
for this segment 20H-2FH. Each one of the 128 bits of
this segment can be directly addressed (0-7FH). Each
of the 16 bytes in this segment can also be addressed
as a byte.
3. Scratch Pad Area: 30H-7FH are available to the user
as data RAM. However, if the data pointer has been
initialized to this area, enough bytes should be left
aside to prevent SP data destruction.
Program Memory
(Read Only)
FFFFH:
64K
Data Memory
(Read/Write)
FFFFH
External
External
EA = 0
External
0FFFH:
4K
0000
EA = 1
Internal
PSEN
Internal
FFH
7FH
80H
00
0000
RD WR
Figure 5. IS89C51 Program and Data Memory Structure
Integrated Silicon Solution, Inc. — 1-800-379-4774
7
MC016-1C
11/21/98