串行数字网络

摘要：本文提供了可以挂接两个或更多数字器件进行通信的串行接口的关键特性。设计工程师可以利用本文给出的表格对各种接口进行比较，根据具体的应用条件，如：信号线数、网络尺寸、速度、距离、抗干扰能力、故障容限和可靠性等，选择适当的接口标准。



  1-Wire I²C SMBus™ SPI™ MICROWIRE/PLUS™ M-Bus (EN1434) CAN (ISO11898) LIN Bus Network Concept single master, mulTIple slaves mulTIple masters, mulTIple slaves mulTIple masters, multiple slaves single master, multiple slaves single master, multiple slaves single master, multiple slaves multiple masters, multiple slaves single master, multiple slaves Number of Signal Lines 1 (IO) 2, (SCL, SDA) 2, (SMBCLK, SMBDAT) 4, (active-low CS, SI, SO, SCK) 4, (active-low CS, DI, DO, SK) 2 (lines can be swapped) 2 (CAN_H, CAN_L, terminated) 1 (LIN) Optional signals N/A N/A SMBSUS#, SMBALERT# N/A N/A N/A 2nd GND, Power, Shield N/A Network Size Up to 300 m (with suitable master circuit) Limited by max. 400pF bus capacitance requirement Limited by max. 400pF bus capacitance requirement N/A (circuit board level) N/A (circuit board level) Max. 350m per segment of max. 250 slaves; max. 180nF 40m @1M bps1000m @ 50k bps (example) Up to 40m, max. 10nF total load Network Interface open drain, resistive or active master pull-up open drain, resistive or active master pull-up open drain, resistive or active master pull-up Push-pull with tristate Push-pull with tristate M to S: voltage drive
S to M: current load Differential open drain/source or open coll./emitter open drain, resistive master pull-up Network Voltage From 2.8 to 6.0 V, device specific From 1.8 to 5.5V, device specific 2.7V to 5.5V From 1.8V to 5.5V, device specific From 1.8V to 5.5V, device specific ~40V VDD-VD (diode drop); ~4.5V max. 8 to 18V Logic Thresholds Vary with network voltage Fixed level: >1.5V, >3.0 V VDD-related level: <30%, >70% of VDD <0.8V, >2.1V VDD-related level: <20% (30%), >70% of VDD (inconsistent) Fixed level: <0.8V, >2.0V; VDD-related level: <20% (30%), >70% (80%) of VDD (inconsistent) Master to slave: 24V, 36V nominalSlave to master: <1.5mA, >11mA Differential: <50mV (recessive), >1.5V (dominant); driver specification VDD-related level: <20%, >80% of VDD (driver spec.)<40%, >60% of VDD (receiver spec.) Transmission LS bit first, half-duplex MS bit first plus Acknowledge bit, half-duplex MS bit first plus Acknowledge bit, half-duplex MS bit first, full-duplex MS bit first, full-duplex LS bit first, half-duplex, acknowledge response MS bit first, half-duplex LS bit first, half-duplex Address Format 56 bits 7 bits, (10 bits defined but not implemented) 7 bits, (10 bits defined but not implemented) N/A N/A 8 bits (primary address), 64 bits (secondary address) Message identifier 11 bits (standard format), 29 bits (extended format) Message identifier 8 bits, including 2 parity bits Network Inventory Automatic, supports dynamic topology change N/A; slave addresses hard-coded in firmware ARP, Address Resolution Protocol (Rev. 2.0 only) N/A; slave select (active-low CS) hard-coded in firmware N/A; slave select (active-low CS) hard-coded in firmware Automatic N/A; message-based protocol, not address based N/A; message-based protocol, not address based Gross Data Rate Standard: ~0 to 16.3k bps Overdrive: ~0 to 142k bps) Standard: ~0 to 100k bps; Fast: ~0 to 400k bps; High-Speed: ~0 to 3.4M bps 10k to 100k bps ~0 to ~10 M bps (device specific) ~0 to ~5 M bps (device specific) 300, 2400, 9600 bps ~0 to 1M bps ~1k to ~20k bps Access Time Standard: ~ 5.4ms Overdrive: ~0.6ms (at maximum speed) Standard: ~95µsFast: ~23µs(at maximum speed) ~95µs @ 100k bps N/A N/A Primary address, 2400 bps: 13.75ms (short frame), 27.5ms (long frame) At 1M bps 19µs (standard) or 39µs (extended) from start of frame to 1st data bit At 20k bps 1.7ms from start of frame to 1st data bit Data Protection 8-bit and 16-bit CRC N/A PEC Packet Error Code (Rev.1.1, 2.0) N/A N/A Even parity, check sum, frames 15-bit CRC, frames, frame acknowledge Check sum, frames Collision Detection Yes, through non-matching CRC Yes (multi-master operation only) Yes (Rev. 2.0 only) N/A N/A Yes ("medium" and "strong" collisions) Yes: CSMA/CD Yes, through check sum Slave supply Parasitic (typical), VDD (exception) VDD only VDD only VDD only VDD only Parasitic and/or local supply VDD only, local or remote source Parasitic only