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

More documents

Recommendations

Info

5.3.20.2 PIC® MCU Initialization Initialization of the PIC12CE674 is straightforward. There are three major functions that need to be properly configured within the PIC12CE674: General Purpose I/O (GPIO) pins Timer0 module A/D Converter module Figure 5.34 shows the pin diagram and names for the PIC12CE674. Figure 5.34 PIC12CE674 Pin Names [42]. The GPIO pins are the six I/O pins that are used to interface the PIC12CE674 to the MCP2515 and sample the analog signals. The PIC® MCU OPTION, TRIS and INTCON registers are used to control the setup of the GPIO pins. For the CAN nodes used in the prototype system, the OPTION register is programmed to disable the internal pull-up resistors on GP0/GP1/GP3. It also configures GP2 to generate an interrupt on the negative edge (to match the MCP2515 device’s active low INT output). The TRIS register, which controls whether each I/O pin is configured as an input or an output, is configured to set GP0/GP1/GP3 as inputs, 173
and GP2 and GP5 as outputs. With the exception of GP4, all of the GPIO pins remain in their initially configured state. GP4 is changed between Input and Output mode, depending upon whether an SPI read or write operation is being performed by the PIC12CE674. The final step of configuring the port pins is to program the INTCON register to enable the interrupt-on-change feature for GP2. This allows the MCP2515 to generate an interrupt to the PIC12CE674. The Timer0 module operation is controlled by the OPTION register and the TMR0 register. The OPTION register contains the control bits for the Timer0 prescaler. The TMR0 register is the counting register for Timer0 and generates an interrupt when it rolls over from 0xFF to 0x00. This register must be reloaded as part of the ISR in order to correctly control the time period between Timer0 interrupts. Initially for each CAN node the timer is set to rollover every 62 ms. This is further expanded to every 500 ms by using a counter. This will reduce the amount of traffic on the CAN bus, but on the down side will reduce the response time to a change in the input. The A/D conversion takes approximately 19 µs for the SPI communication to write the A/D result to the MCP2515 transmit buffer. Then, the conversion sends the RTS command, which requires approximately 409 µs to complete for a total of approximately 428 µs for the ISR to execute. The Timer0 module is configured to use the FOSC/8 option for the conversion clock, which gives a TAD value of 2 µs and an overall conversion time of 19 µs (TAD * 9.5). This is more than fast enough compared to the amount of time spent on SPI communications during the ISR. 174
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 and 112:
For the initial prototype design pr
Page 113 and 114:
the ID of 31 transmits a ‘0’ (d
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: Yes Perform A/D Conversion on AN0 W
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 ...

Create successful ePaper yourself

Delete template?

Save as template?