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參數(shù)資料
| 型號： | DS87C530 |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | EPROM/ROM Micro with Real Time Clock(帶實(shí)時時鐘的EPROM/ROM高速微控制器) |
| 中文描述： | EPROM微控制器，帶有實(shí)時時鐘 |
| 文件頁數(shù)： | 14/41頁 |
| 文件大?。?/td> | 437K |
| 代理商： | DS87C530 |
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DS87C530/DS83C530
070898 14/41
STRETCH MEMORY CYCLE
The DS87C530/DS83C530 allows software to adjust
the speed of off–chip data memory access. The micro-
controller is capable of performing the MOVX in as few
as two instruction cycles. The on–chip SRAM uses this
speed and any MOVX instruction directed internally
uses two cycles. However, the time can be stretched for
interface to external devices. This allows access to both
fast memory and slow memory or peripherals with no
glue logic. Even in high–speed systems, it may not be
necessary or desirable to perform off–chip data memory
access at full speed. In addition, there are a variety of
memory mapped peripherals such as LCDs or UARTs
that are slow.
The Stretch MOVX is controlled by the Clock Control
Register at SFR location 8Eh as described below. It
allows the user to select a Stretch value between zero
and seven. A Stretch of zero will result in a two machine
cycle MOVX. A Stretch of seven will result in a MOVX of
nine machine cycles. Software can dynamically change
this value depending on the particular memory or
peripheral.
On reset, the Stretch value will default to a one resulting
in a three cycle MOVX for any external access. There-
fore, off–chip RAM access is not at full speed. This is a
convenience to existing designs that may not have fast
RAM in place. Internal SRAM access is always at full
speed regardless of the Stretch setting. When desiring
maximum speed, software should select a Stretch value
of zero. When using very slow RAM or peripherals,
select a larger Stretch value. Note that this affects data
memory only and the only way to slow program memory
(ROM) access is to use a slower crystal.
Using a Stretch value between one and seven causes
the microcontroller to stretch the read/write strobe and
all related timing. Also, setup and hold times are
increased by 1 clock when using any Stretch greater
than 0. This results in a wider read/write strobe and
relaxed interface timing, allowing more time for
memory/peripherals to respond. The timing of the vari-
able speed MOVX is in the Electrical Specifications.
Table 4 shows the resulting strobe widths for each
Stretch value. The memory Stretch uses the Clock Con-
trol Special Function Register at SFR location 8Eh. The
Stretch value is selected using bits CKCON.2–0. In the
table, these bits are referred to as M2 through M0. The
first Stretch (default) allows the use of common 120 ns
RAMs without dramatically lengthening the memory
access.
DATA MEMORY CYCLE STRETCH VALUES
Table 4
CKCON.2–0
M2
M1
M0
MEMORY CYCLES
RD OR WR STROBE
WIDTH IN CLOCKS
STROBE WIDTH TIME
@ 33 MHz
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
2 (forced internal)
3 (default external)
4
5
6
7
8
9
2
4
8
12
16
20
24
28
60 ns
121 ns
242 ns
364 ns
485 ns
606 ns
727 ns
848 ns
DUAL DATA POINTER
The timing of block moves of data memory is faster
using the Dual Data Pointer (DPTR). The standard 8051
DPTR is a 16–bit value that is used to address off–chip
data RAM or peripherals. In the DS87C530/DS83C530,
the standard data pointer is called DPTR, located at
SFR addresses 82h and 83h. These are the standard
locations. Using DPTR requires no modification of stan-
dard code. The new DPTR at SFR 84h and 85h is called
DPTR1. The DPTR Select bit (DPS) chooses the active
pointer. Its location is the lsb of the SFR location 86h. No
other bits in register 86h have any effect and are 0. The
user switches between data pointers by toggling the lsb
of register 86h. The increment (INC) instruction is the
fastest way to accomplish this. All DPTR–related
instructions use the currently selected DPTR for any
activity. Therefore it takes only one instruction to switch
from a source to a destination address. Using the Dual
Data Pointer saves code from needing to save source
and destination addresses when doing a block move.
The software simply switches between DPTR and 1
once software loads them. The relevant register loca-
tions are as follows.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| DS87C530_05 | 制造商:DALLAS 制造商全稱:Dallas Semiconductor 功能描述:EPROM/ROM Microcontrollers with Real-Time Clock |
| DS87C530_1 | 制造商:DALLAS 制造商全稱:Dallas Semiconductor 功能描述:EPROM/ROM Micro with Real Time Clock |
| DS87C530+ECL | 制造商:Maxim Integrated Products 功能描述:MICRO OTP RTC 33MHZ 52P TQFP PB-FRR - Trays |
| DS87C530-ECL | 功能描述:8位微控制器 -MCU EPROM MCU w/RTC RoHS:否 制造商:Silicon Labs 核心:8051 處理器系列:C8051F39x 數(shù)據(jù)總線寬度:8 bit 最大時鐘頻率:50 MHz 程序存儲器大小:16 KB 數(shù)據(jù) RAM 大小:1 KB 片上 ADC:Yes 工作電源電壓:1.8 V to 3.6 V 工作溫度范圍:- 40 C to + 105 C 封裝 / 箱體:QFN-20 安裝風(fēng)格:SMD/SMT |
| DS87C530-ECL+ | 功能描述:8位微控制器 -MCU EPROM MCU w/RTC RoHS:否 制造商:Silicon Labs 核心:8051 處理器系列:C8051F39x 數(shù)據(jù)總線寬度:8 bit 最大時鐘頻率:50 MHz 程序存儲器大小:16 KB 數(shù)據(jù) RAM 大小:1 KB 片上 ADC:Yes 工作電源電壓:1.8 V to 3.6 V 工作溫度范圍:- 40 C to + 105 C 封裝 / 箱體:QFN-20 安裝風(fēng)格:SMD/SMT |
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