DESIGN OF A CUSTOM ASIC INCORPORATING CAN™ AND 1 ...

More documents

Recommendations

Info

A final proposed method is based upon an automatic node discovery process to identify nonconfigured CAN nodes directly in a CANopen® system [41]. Every CAN node in the prototype system described in this dissertation consists of the following components: Microchip PIC12CE674 [42] microcontroller, Microchip MCP2515 stand-alone CAN Controller [43 – 44], and a Microchip MCP2551 high-speed CAN transceiver [45]. A simplified block diagram of the CAN components on each node is shown in Figure 4.5. The use of the PIC® microcontroller allows each node to have a unique address, stored in EEPROM, so a number of different devices can coexist on the same network. This would allow communication from a 1 – Wire® device (message by address) to a specific CAN node which would have a unique address on the CAN network. By storing the node address in EEPROM, this allows the node to not only be re-addressed if the addition of more nodes on the CAN bus is required, but also ensures that the node address value is retained in the event of power loss. Message IDs must be unique on a single CAN bus, otherwise two nodes would continue transmission beyond the end of their arbitration field (ID) causing an error (see Figures 3.3 and 3.4). The choice of IDs for messages is often done simply on the basis of identifying the type of data and the sending node; however, as the message ID is also used as the message priority, this can lead to poor real-time performance. For example, consider an 11-bit ID CAN network, with two nodes with IDs of 31 (binary representation, 00000011111) and 32 (binary representation, 00000100000). If these two nodes transmit at the same time, each will transmit the first five zeros of their ID with no arbitration decision being made. When the sixth bit is transmitted, the node with the ID of 32 transmits a ‘1’ (recessive) for its ID, and the node with 87
the ID of 31 transmits a ‘0’ (dominant) for its ID. When this happens, the node with the ID of 32 will realize that it lost its arbitration, and allow the node with ID of 31 to continue its transmission. This ensures that the node with the lower bit value will always win the arbitration. So to summarize, with properly configured message acceptance filters and masks, messages sent from the 1 – Wire® Master will be properly directed to the appropriate CAN node. Figure 4.5 CAN node components simplified block diagram [45 – 47]. By configuring hardware acceptance filters in the CAN Controller on each node, this reduces the probability of data overrun conditions on any one CAN node. The number of acceptance filters varies with different CAN Controllers and manufacturers. If properly configured for each CAN node, the acceptance filters could be used as a method of allowing only certain types of messages to be accepted by each individual CAN node. While receiving a CAN message, the identifier (and sometimes even the data) can be compared to a configured filter. Only if the incoming message matches the filter does the message get stored into a receive buffer on that particular CAN node. Thus it is possible to reduce the processing load of the host controller. Typically on a CAN Controller the message acceptance filter is controlled by two 8 – bit wide registers: usually named Acceptance Code Register (ACR) and Acceptance Mask Register (AMR). The eight most significant bits of the identifier of the CAN message 88
Page 1 and 2:
DESIGN OF A CUSTOM ASIC INCORPORATI
Page 3 and 4:
ABSTRACT The vast majority of today
Page 5 and 6:
LIST OF ABBREVIATIONS AND SYMBOLS A
Page 7 and 8:
ISO International Organization for
Page 9 and 10:
SI Serial In SO Serial Out SOF Star
Page 11 and 12:
ACKNOWLEDGEMENTS I would like to ex
Page 13 and 14:
2.4 Types of Devices...............
Page 15 and 16:
4.3.5 Communication Speed Different
Page 17 and 18:
5.3.21.1 Synchronization Test (test
Page 19 and 20:
5.3 Resource Utilization...........
Page 21 and 22:
LIST OF FIGURES 2.1 1 - Wire® Netw
Page 23 and 24:
4.12 Read-Data Time Slot...........
Page 25 and 26:
6.4 DS1996 Address Registers ......
Page 27 and 28:
manufacturing process. Structured o
Page 29 and 30:
describes the 1 - Wire® and CAN co
Page 31 and 32:
2.2 1 - Wire® Overview The basis o
Page 33 and 34:
All 1 - Wire® masters described in
Page 35 and 36:
attachments, microcontroller with b
Page 37 and 38:
Figure 2.3 Bidirectional port pin w
Page 39 and 40:
2.3.3 Synthesizable 1 - Wire® Bus
Page 41 and 42:
Figure 2.7 UART/RS232 Serial Port I
Page 43 and 44:
hardware. Through control registers
Page 45 and 46:
Table 2.2 1 - Wire® Bus Operations
Page 47 and 48:
2.3.6 1 - Wire® Search Algorithm F
Page 49 and 50:
detected. This ‘read two bits’
Page 51 and 52:
in Figure 2.15. Alternatively, the
Page 53 and 54:
of the bit, then write the desired
Page 55 and 56:
2.4.2 Device Functions and Typical
Page 57 and 58:
and development (R&D) investments b
Page 59 and 60:
2.5 Network Types and Precedents As
Page 61 and 62: 2.5.2 1 - Wire® Network Topologies
Page 63 and 64: 2.5.3 1 - Wire® Network Limitation
Page 65 and 66: with a single selected slave. If an
Page 67 and 68: user group was founded in March of
Page 69 and 70: protocol on multiple media for maxi
Page 71 and 72: ecessive bit and the monitored stat
Page 73 and 74: specification: Start-Of-Frame, Arbi
Page 75 and 76: Cyclic Redundancy Check (CRC) Field
Page 77 and 78: Arbitration FieldThe Arbitration Fi
Page 79 and 80: SOF SOF Bit 28 Bit 27 Arbitration f
Page 81 and 82: Afterwards it starts transmitting s
Page 83 and 84: Figure 3.9 Structure of the Interfr
Page 85 and 86: error occurs, an Error Frame is gen
Page 87 and 88: Table 3.4 Error Flag Output Timing
Page 89 and 90: 3.5.2 Error-Passive A node becomes
Page 91 and 92: where tNBT is the Nominal Bit Time
Page 93 and 94: Figure 3.12 Propagation Delay Betwe
Page 95 and 96: 3.6.4 Synchronization t t t t (3.
Page 97 and 98: opposite value is inserted into the
Page 99 and 100: many systems, the bus length will b
Page 101 and 102: CHAPTER 4 THE CHALLENGES OF INTERFA
Page 103 and 104: In June 2004, Maxim Integrated Prod
Page 105 and 106: Wearable sensor technology is a new
Page 107 and 108: In traditional bus architectures, o
Page 109 and 110: Figure 4.3 Centralized arbiter with
Page 111: For the initial prototype design pr
Page 115 and 116: Recently, a technique has been prop
Page 117 and 118: procedure, then the address claim p
Page 119 and 120: paradigms are prevalent in the desi
Page 121 and 122: systems possess a higher flexibilit
Page 123 and 124: fixed identifier and hence a fixed
Page 125 and 126: 348sm Cm 47 8 smbit 11-bit hea
Page 127 and 128: est-case latency occurs when the bu
Page 129 and 130: to break the 1 - Wire® network int
Page 131 and 132: ow, is most critical for power deli
Page 133 and 134: computations have device-specific p
Page 135 and 136: Table 4.7 Example results with N 2
Page 137 and 138: 4.3.5 Communication Speed Different
Page 139 and 140: anging” a port pin on a microproc
Page 141 and 142: From Figure 5.1, the block I/O pins
Page 143 and 144: 5.2.2 Command Register In addition
Page 145 and 146: specifies the selected bit value to
Page 147 and 148: with i > m. This process is repeate
Page 149 and 150: Figure 5.6 Interrupt Register. OW_
Page 151 and 152: the INTR pin will be pulled high si
Page 153 and 154: master reset occurs. Table 5.2 show
Page 155 and 156: EN_FOW: Enable Force One Wire. Sett
Page 157 and 158: READ_ROM - Used to read the 64-bit
Page 159 and 160: 5.2.8.1 Single Search ROM (single_s
Page 161 and 162: 5.2.8.3 Scratchpad Memory (scratchp
Page 163 and 164:
5.2.8.4 Command Recognition (cmd_re
Page 165 and 166:
TBF - The Transmit Buffer provides
Page 167 and 168:
compensate for the propagation dela
Page 169 and 170:
Figure 5.15 CAN Module memory map [
Page 171 and 172:
‘0’, fast speed mode will be us
Page 173 and 174:
COMP-SEL: Comparator Select. When t
Page 175 and 176:
Figure 5.18 CAN Status Register. B
Page 177 and 178:
that buffer is given to the CPU and
Page 179 and 180:
Acceptance Mask Registers (accepted
Page 181 and 182:
SJW1, SJW0: Synchronization Jump Wi
Page 183 and 184:
TSEG22 - TSEG10: Time Segment Bits.
Page 185 and 186:
The transmit clock (ttxclk) is used
Page 187 and 188:
5.3.13 CAN Module Transmit Buffer I
Page 189 and 190:
Figure 5.28 CAN Transmit Data Segme
Page 191 and 192:
5.3.20 CAN Node Overview As stated
Page 193 and 194:
Read Digital InputsRead the value o
Page 195 and 196:
the clock high time is either 5 µs
Page 197 and 198:
Yes Perform A/D Conversion on AN0 W
Page 199 and 200:
and GP2 and GP5 as outputs. With th
Page 201 and 202:
external INT pin, and then branches
Page 203 and 204:
Read MCP2515 Rx Buffer for Digital
Page 205 and 206:
When a valid message is received, t
Page 207 and 208:
Table 5.19 Resource Utilization. Re
Page 209 and 210:
For this test, only one CAN node wa
Page 211 and 212:
an Error Frame to be generated. Aft
Page 213 and 214:
messages, acknowledge messages, or
Page 215 and 216:
5.3.21.4 Send Basic Frame Test (sen
Page 217 and 218:
going from one node to 30 nodes (se
Page 219 and 220:
Table 6.1 Resource Utilization. Rev
Page 221 and 222:
6.2.1 Test Verification and Overvie
Page 223 and 224:
has read access to this register. T
Page 225 and 226:
system configuration used for this
Page 227 and 228:
or not depends on the number of rec
Page 229 and 230:
6.4. There are two receiving CAN no
Page 231 and 232:
CHAPTER 7 CONCLUSIONS AND FUTURE WO
Page 233 and 234:
a communication bus reset will occu
Page 235 and 236:
For the synthesizable CAN Controlle
Page 237 and 238:
additional CAN nodes were added to
Page 239 and 240:
Fall-Through Stack A LOW level on t
Page 241 and 242:
In conclusion, the prototype system
Page 243 and 244:
REFERENCES [1] IBM ASIC Products Ap
Page 245 and 246:
[22] “CAN - a brief tutorial for
Page 247 and 248:
[44] Microchip MCP2515 - Stand-Alon
Page 249 and 250:
[67] K. Tindell and A. Burns, “Gu
Page 251 and 252:
[88] “Verilog - A Language Refere
show all

DESIGN OF A CUSTOM ASIC INCORPORATING CAN™ AND 1 ...

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?