IC693ACC303IC693ACC303
当CPU处理前台任务时，USB的传输可在后台进行；后台中断服务程序和前台主程序循环之间的数据交换可以通过事件标志和数据缓冲区来实现。当PDIUSBD12从USB收到一个数据包，即对CPU产生一个中断请求，CPU立刻响应中断。在中断服务程序中，固件将数据包从PDIUSBD12内部缓冲区移到循环数据缓冲区，并将PDIUSBD12的内部缓冲区清零，以便接收新的数据包，使CPU可以继续执行当前的前台任务直到完成。本文利用PDIUSBD12的端点1进行命令的传输和应答，端点1每次接收计算机发送过来的8 B指令，其指令格式如表2所示。例如，接收到十六进制码52 01 00 03 00 07 00 50，表示读24C01器件从03字节开始的7个字节的数据。52H为R的ASCII码，57H为W的ASCII码。端点2用于数据的传输。
PLC的发展趋势
随着PLC应用领域日益扩大，PLC技术及其产品结构都在不断改进，功能日益强大，性价比越来越高。
（1）、在产品规模方面，向两极发展。一方面，大力发展速度更快、性价比更高的小型和超小型PLC。以适应单机及小型自动控制的需要。另一方面，向高速度、大容量、技术完善的大型PLC方向发展。随着复杂系统控制的要求越来越高和微处理器与计算机技术的不断发展，人们对PLC的信息处理速度要求也越来越高，要求用户存储器容量也越来越大。
（2）、向通信网络化发展
PLC网络控制是当前控制系统和PLC技术发展的潮流。PLC与PLC之间的联网通信、PLC与上位计算机的联网通信已得到广泛应用。目前，PLC制造商都在发展自己的通信模块和通信软件以加强PLC的联网能力。各PLC制造商之间也在协商通用的通信标准，以构成更大的网络系统。PLC已成为集散控制系统（DCS）*的组成部分。
郑娟萍
厦门仲鑫航自动化设备有限公司
（3）、向模块化、智能化发展
为满足工业自动化各种控制系统的需要，近年来，PLC厂家先后开发了不少新器件和模块，如智能I/O模块、温度控制模块和专门用于检测PLC外部故障的智能模块等，这些模块的开发和应用不仅增强了功能，扩展了PLC的应用范围，还提高了系统的可靠性。
（4）、编程语言和编程工具的多样化和标准化
多种编程语言的并存、互补与发展是PLC软件进步的一种趋势。 PLC厂家在使硬件及编程工具换代频繁、丰富多样、功能提高的同时，日益向MAP(制造自动化协议)靠拢，使PLC的基本部件，包括输入输出模块、通信协议、编程语言和编程工具等方面的技术规范化和标准化。
Ashcroft Model: 250-3074 Guage. New Old Stock. No Box
Ashcroft Test Guage. 0 - 300 PSI. No Model Number
Ashcroft Type 1008 316 SS Guage, 1/4" NPT, 63mm
HPS MKS100312906-W NW50 AL CLAMP W/WASHER NEW
Marsh: J2440 General Service Gauge. 2.0 STB-B, 1/8M, 0/15 PSI. New Old Stock
MARSH J7654P 63MM SEVB 1/4 NPT 0-200PSI KPA GAUGE. New Old Stock
Ashcroft: 35-1009AW-02L-1000# General Service Guage. New Old Stock
Sensotec: 060-3147-01 GM Digital Display / Signal Conditioner, In Altered Box
Marshalltown Instruments Model: G23868 Press. Gauge. New Old Stock
Weiss Instruments: 9VU35 INDUSTRIAL GLASS THERMOMETER. New Old Stock *W2
Dwyer 3000 Series, Model: 3025 Photohelic Guage
Sensotec / Honeywell Model: 060-H919-04. Order Code: FPG2DN,2P5B6M
Hydrocraft: HC1V-002S Liquid Filled Guage. -30 in Hg to +30 PSI. New Old Stk
MKS Instruments Model: 621A Signal Conditioner. PN: 621A11TBFH. Genly Used J
Marsh / Bellofram: J4648 Guage. 2.5 STD, 1/4 NPT
Custom Controls Sensor Inc. Model: 604P12 Pressure Switch. 3000 PSIG
SENSOTEC 41/8750-04-02 LOAD CELL RANGE: 100 LBS 10.0 VDC W
Viatran Model: 5715BCSTFYMZU Pressure Transmitter. Range: 0 - 10000 PSI W
Aschcroft Model: 25W1001TH 01B XUC Brass Guage. 2? Case. New Old Stock J
ROBERTSHAW UNI-LINE 2420-001 1 1/2" GAUGE QTY 2 NEW
MKS Instruments Type: 600A Partial Pressure Transducer
Pacific Scientific / Precision Model: G425FSD04S Guage. New Old Stock R
Eugene Ernst Products / EEP: Clear No. 500 Standard Glass Guage. New Old Stock
Wika: 0 - 10,000 PSI Liquid Filled Gauge. 316 SS Tube and Connection. No PN
NoShok Model: 25.120.100. PSI.FPT.? NPT Control Guage. New Old Stock
Ametek / USG Model: 70MDD Pressure Guage. New Old Stock
T-Hydronics: TH-MF Pressure Transducer. P/N: 005168-7. Range: 0-7500 PSIG W
Process Level Technology MAG-GAGE, MG with Float and MGS-500EX
MKS Instruments: 122AA-00001AB Pressure Transducer
MARSHALL TOWN GG-25100 L4 GG25100L4 100PSI 1/2" GUAGE
Patriot 65998-SP100-9410000G Pressure Transducer. 0 - 10000 PSIG. Used
Sensotec Model: AG-200, P/N: 060-9965-23 ACCU-GAGE Controller W
Matheson Regulator Assembly w/ 4384 and 3455 Valves
MKS / Baratron: 122A-11063 Pressure Transducer. 10 TORR. Input: +/- 15VDC
2-1/2" DRY 1/2 NPT BRASS LOWER 0-100 PSI/KPA/BAR GUAGE
MKS / HPS Products Model: V-100-IM-MR-NV Valve. Nw100 Valve
Dillon Quantrol Smart S-Beam. Part Number: 49753-0055. Capacity: 550 lbf W
SENSOTEC 41/8937-01-01 LOAD CELL RANGE 10000 LBS 10.0 VDC W
ASHCROFT 25W1001TH 01B XUC PANEL MOUNT GAUGE NEW
MKS / HPS Division Model: NW50 AL Clamp w/ Washer
WEKSLER MODEL: BY12YPT4LW Pressure Gauge 2.5" (New Old Stock) *
(8) SPAN / TYLAN 0-4000 PSI Pressure Gauge, new =
SI Span Instruments: IPS122 Press. Guage w/Control Box
Kulite Semiconductor: HKS-375-5000SG Pressure Transducer. Unused. Short Wire
Marshalltown Instruments: Y1211 Industrial Thermometer. New Old Stock
Viatran Model: 5715BCSNHTFYAZU Pressure Transmitter. Range: 0 - 3000 PSI W
Viatran Model: 5715BH6X2960 Pressure Transmitter. Range: 0 - 7500 PSI W
SENSOTEC Z/8809-03 20000 PSIG 10.0 VDC 2.9 MV/V W
Sensotec Model: 060-6831-00 Load Cell. W
MKS / Baratron: 122B-14670 Pressure Transducer
Entran Model: ELF-500-56B-5, "EL Type" Load Cell
ASHCROFT 8080000 THERMOMETER 8544-152 60 TO 260 F DRESSER IND TYPE A AISLE BB
2.5" Dry, 1/4 NPT, Brass Pressure Guages NEW
MKS Instruments Model 652B-DD Exhaust Throttle Valve.
Honeywell Sensotec P/N: 060-K107-01 Non-Aplified Transducer. Model: WPK W
Kulite Semiconductor: BME-1100-1000A-A-4-1 Pressure Transducer. New Old Stock
Victor Supply Company Model: SR250D Welding Guage
Kulite Semiconductor: HKS-375-5000SG Pressure Transducer. New Old Stock
WIKA TYPE: 213.53 2.5 1000PSI 9767126 1/2" GUAGE. New Old Stock
Viatran Model: 345BHGCMX251 Pressure Transducer w/ Cable. Range: 0-7500 PSIG W
Leeds & Northrup: 2610-100-12-2-01-300-802-809 Pressure Transmitter. New Old Stk
Ashcroft Test Guage, Temerature Compensated. No Mdl #
Interface LBM Compression Load Button Model: LBM-5K with TEDS Installed
Interface LBM Compression Load Button Model: LBM-10K-468 with TEDS Installed
Interface LBM Compression Load Button Model: LBM-20K with TEDS Installed
Aschcroft Industrial Duralife Gauge, Type: 1009. New Old Stock
MKS Instruments Type: TC-1A Thermocouple Vacuum Guage
MKS Instruments Type: TC-1A Thermocouple Vacuum Guage
MKS / HPS Model: 162-0016T Standard Pneumatic Single Stage Unheated Valve W2
Marsh: J4020 Guage. 2.5 STD 1/8" NPT. 30X 300 INHGXPSI & KPA. New Old Stock
Transducer Techniques Model: DPM 3 Control Panel W2
Transducer Techniques Model: DPM-3 Plug & Play,Control Panel. IEEE 1451.4 W2
Wika: 232.53 Guage. P/N: 9768327. 2.5", 100PSI, ?" CBM/FF. New Old Stock
Kulite Semiconductor XTS-1-190-2000A Press. Transducer. New Old Stock
MKS Instruments Model 244C-1-VP0 Pressure/Flow Cntlr.
MKS / Baratron: 127AA-000.1C Pressure Transducer. 1 TORR. Input: +/- 15VDC
Datametrics Barocel Pressure Sensor, PN: 600A-10T-R12-
Ashcroft Model: 601010A-04L 0/15# & 0/100 General Service Guage. ? NPT Lower W
Transducer Techniques: LBO-30K Low Profile Compression Load Cell. 30K Lbs
McDaniel Controls FGI Glycerin Filled Pressure Guage
LDS SC-7C WHITEY 10EK907 5.55 X 10-7 ATM HELIUM LEAK
LDS SC-7C WHITEY 10EK907 5.91 X 10-7 ATM HELIUM LEAK
Winter's 0 - 100 PSI & KPA Code 904 Guage. 2.5 X ? NPT. New Old Stock
T-HYDRONICS MODEL: A005168-7.5K PRESSURE TRANSDUCER *W2
Dwyer Cat. 2-5001 Minihelic II Differential Pressure Guage. Cat. #: N23T W
Dwyer Cat. N44K Minihelic II Differential Pressure Guage. W
Magnehelic: 2002C Pressure Guage. 0 - 2 Inches of Water. 15 PSIG Max. Press W
Eugene Ernst Prod. / EEP: Clear No. 500 Std Glass Guage. OD: 8?. New Old Stock
Ashcroft Model: 12D Metal Case Thermometer. 50 - 300° F. New Old Stock No Bo
MKS Baratron Model: 122BA-00100DB Pressure Transducer
(2) DWYER series 1800 Pressure Switch, new =
Omega Engineering Model: PX602 Thin Film Pressure Sensor W2
WIKA 8610007 3133890 TRANSMITTER S-10 17955838 NEW
AMETEK P844U PRESSURE GAUGE 30 PSI NEW IN BOX
Omega Engineering Model: PIX314-050A5V General Pressure Transmitter W
Spir Star: 5/4HT High Pressure Hose. 1.5 Feet, Max PSI: 15000. 1/4 NPT Male W
Viatran Model: 345BPSDNYM Pressure Transducer. Range: 0-15000 PSIG
Heise / Dresser Model: CMM-125153 0 - 10,000 PSI Test / Pressure Guage W
Cronatron CW2004 Heavy Duty 2 Stage Press. Reg. New
SI SPAN INSTRUMENTS IPS 122 TYPE 1 GUAGE 12 WATT NEW
Druck Model PTX 510 Pressure Transducer. 5000 PSI, 9 - 30Vdc
Rosemount Model: 3051 Pressure Transmitter. TA3A2B21AB4E8M5Q4. 800PSIA. W2
STANDARD METER LAB LFE: AH-0103-0000 O204 LASER GUAGE
STANDARD METER LAB LFE: AH-0103-0000 O204 PHOTOCURRENT
AMETEK DUPONT S2204 FILTER KIT QTY (5) NEW
MKS PARTIAL PRESSURE TRANSDUCER TYPE 600A PPT-1A-100FC
Marshalltown Instruments: G10172. Gauge. 4?, ? Bottom Conn. New Old Stock
Marsh Model: J7220RP GAUGE *W2
Sensotec: 060-6827-04 Inline Amplifier. Input: 18-28V DC. Out: +/- 10 VDC
Weiss Instruments: LF25S-1 Glycerine Filled Gauge.
BS&S Safety Systems Ruture Disk (Bursting Disc), P/N: CH-0-000-2-000. W
MKS / Baratron: 122B-14670 Pressure Transducer
NoShok Model: 25.400.1500 PSI 1/4 Bottom Control Guage. New Old Stock
UTHE Technology: 27PT Standard Wedge Transducer. Freq: 64.0. New Old Stock
Kulite Semiconductor: BME-1100-1000A-A-X-1 Pressure Transducer. New Old Stock
Numatics Model: 214-194 Liquid Filled Pressure Guage. New Old Stock.
MKS Type 247C Instruction Manual, PN: 195-110354A-7/87
Ametek / USG Model: 146002 Pressure Guages. 60 PSI, 1/8 NPT, New Old Stock
BRC Model: W101 4" Gauge
Victor Model: SR4K Inert Gas Weld Gauge. 5500 PSIG. Good Used Stock
Rosemount Model: 1151DP3E22 Pressure Transmitter. Spares Unused Old Stock
TRANE AMETEK GAG 0105 GAG0105 1000PSI 153619 GAUGE
Viatran Model: 571AZ2ZSTFYA2U Pressure Transmitter. Range: 0 - 1500 PSI W
MKS / NGS PPT Residual Gas Analyzer, PPT-1A-100FC
ASHCROFT 20W1005 Steel Polycarbonate Brass Gauge. New Old Stock
Ashcroft Model: 1001 XUC Guage, 1/4" NPT
Ametek 1980 Pressure Guage. New in box
MKS Instruments Model: 919 Hot Cathode Controller
MKS Instruments: 227AA-00001-SPFTG-8VCO Transducer
Sensotec Model: AG-200, P/N: 060-9965-23 ACCU-GAGE Controller Good Used Stock
Helium Leak Testing, Inc / QHe Model: HLT-7DT Leak Detector. S/N: 2386
Helium Leak Testing, Inc / QHe Model: HLT-7DT Leak Detector. S/N: 2387
Helium Leak Testing, Inc / QHe Model: 0981 Leak Detector. S/N: LLE9027
Pressure Transducer: GP:50 Pressure Transducer. Part #: 311-B. 0 - 20 PSIV
MKS Instruments: 227AA-00001A Pressure Transducer
Helium Leak Testing, Inc / QHe Model: SC-8D Leak Detector. S/N: EBBB6007
Helium Leak Testing, Inc / QHe Model: SC-8D Leak Detector. S/N: 8836
Western Accu-Trol Model: RHP-2-4 Compressed Gas Regulator
DC MILLIAMPERES 0-1 2031-4842001 GAUGE PLASTIC NEW
