1/* SPDX-License-Identifier: GPL-2.0 */ 2/* 3 * Driver definitions for the FTDI USB Single Port Serial Converter - 4 * known as FTDI_SIO (Serial Input/Output application of the chipset) 5 * 6 * For USB vendor/product IDs (VID/PID), please see ftdi_sio_ids.h 7 * 8 * 9 * The example I have is known as the USC-1000 which is available from 10 * http://www.dse.co.nz - cat no XH4214 It looks similar to this: 11 * http://www.dansdata.com/usbser.htm but I can't be sure There are other 12 * USC-1000s which don't look like my device though so beware! 13 * 14 * The device is based on the FTDI FT8U100AX chip. It has a DB25 on one side, 15 * USB on the other. 16 * 17 * Thanx to FTDI (http://www.ftdichip.com) for so kindly providing details 18 * of the protocol required to talk to the device and ongoing assistence 19 * during development. 20 * 21 * Bill Ryder - bryder@sgi.com formerly of Silicon Graphics, Inc.- wrote the 22 * FTDI_SIO implementation. 23 * 24 */ 25 26/* Commands */ 27#define FTDI_SIO_RESET 0 /* Reset the port */ 28#define FTDI_SIO_MODEM_CTRL 1 /* Set the modem control register */ 29#define FTDI_SIO_SET_FLOW_CTRL 2 /* Set flow control register */ 30#define FTDI_SIO_SET_BAUD_RATE 3 /* Set baud rate */ 31#define FTDI_SIO_SET_DATA 4 /* Set the data characteristics of 32 the port */ 33#define FTDI_SIO_GET_MODEM_STATUS 5 /* Retrieve current value of modem 34 status register */ 35#define FTDI_SIO_SET_EVENT_CHAR 6 /* Set the event character */ 36#define FTDI_SIO_SET_ERROR_CHAR 7 /* Set the error character */ 37#define FTDI_SIO_SET_LATENCY_TIMER 9 /* Set the latency timer */ 38#define FTDI_SIO_GET_LATENCY_TIMER 0x0a /* Get the latency timer */ 39#define FTDI_SIO_SET_BITMODE 0x0b /* Set bitbang mode */ 40#define FTDI_SIO_READ_PINS 0x0c /* Read immediate value of pins */ 41#define FTDI_SIO_READ_EEPROM 0x90 /* Read EEPROM */ 42 43/* Interface indices for FT2232, FT2232H and FT4232H devices */ 44#define INTERFACE_A 1 45#define INTERFACE_B 2 46#define INTERFACE_C 3 47#define INTERFACE_D 4 48 49 50/* 51 * BmRequestType: 1100 0000b 52 * bRequest: FTDI_E2_READ 53 * wValue: 0 54 * wIndex: Address of word to read 55 * wLength: 2 56 * Data: Will return a word of data from E2Address 57 * 58 */ 59 60/* Port Identifier Table */ 61#define PIT_DEFAULT 0 /* SIOA */ 62#define PIT_SIOA 1 /* SIOA */ 63/* The device this driver is tested with one has only one port */ 64#define PIT_SIOB 2 /* SIOB */ 65#define PIT_PARALLEL 3 /* Parallel */ 66 67/* FTDI_SIO_RESET */ 68#define FTDI_SIO_RESET_REQUEST FTDI_SIO_RESET 69#define FTDI_SIO_RESET_REQUEST_TYPE 0x40 70#define FTDI_SIO_RESET_SIO 0 71#define FTDI_SIO_RESET_PURGE_RX 1 72#define FTDI_SIO_RESET_PURGE_TX 2 73 74/* 75 * BmRequestType: 0100 0000B 76 * bRequest: FTDI_SIO_RESET 77 * wValue: Control Value 78 * 0 = Reset SIO 79 * 1 = Purge RX buffer 80 * 2 = Purge TX buffer 81 * wIndex: Port 82 * wLength: 0 83 * Data: None 84 * 85 * The Reset SIO command has this effect: 86 * 87 * Sets flow control set to 'none' 88 * Event char = $0D 89 * Event trigger = disabled 90 * Purge RX buffer 91 * Purge TX buffer 92 * Clear DTR 93 * Clear RTS 94 * baud and data format not reset 95 * 96 * The Purge RX and TX buffer commands affect nothing except the buffers 97 * 98 */ 99 100/* FTDI_SIO_SET_BAUDRATE */ 101#define FTDI_SIO_SET_BAUDRATE_REQUEST_TYPE 0x40 102#define FTDI_SIO_SET_BAUDRATE_REQUEST 3 103 104/* 105 * BmRequestType: 0100 0000B 106 * bRequest: FTDI_SIO_SET_BAUDRATE 107 * wValue: BaudDivisor value - see below 108 * wIndex: Port 109 * wLength: 0 110 * Data: None 111 * The BaudDivisor values are calculated as follows: 112 * - BaseClock is either 12000000 or 48000000 depending on the device. 113 * FIXME: I wish I knew how to detect old chips to select proper base clock! 114 * - BaudDivisor is a fixed point number encoded in a funny way. 115 * (--WRONG WAY OF THINKING--) 116 * BaudDivisor is a fixed point number encoded with following bit weighs: 117 * (-2)(-1)(13..0). It is a radical with a denominator of 4, so values 118 * end with 0.0 (00...), 0.25 (10...), 0.5 (01...), and 0.75 (11...). 119 * (--THE REALITY--) 120 * The both-bits-set has quite different meaning from 0.75 - the chip 121 * designers have decided it to mean 0.125 instead of 0.75. 122 * This info looked up in FTDI application note "FT8U232 DEVICES \ Data Rates 123 * and Flow Control Consideration for USB to RS232". 124 * - BaudDivisor = (BaseClock / 16) / BaudRate, where the (=) operation should 125 * automagically re-encode the resulting value to take fractions into 126 * consideration. 127 * As all values are integers, some bit twiddling is in order: 128 * BaudDivisor = (BaseClock / 16 / BaudRate) | 129 * (((BaseClock / 2 / BaudRate) & 4) ? 0x4000 // 0.5 130 * : ((BaseClock / 2 / BaudRate) & 2) ? 0x8000 // 0.25 131 * : ((BaseClock / 2 / BaudRate) & 1) ? 0xc000 // 0.125 132 * : 0) 133 * 134 * For the FT232BM, a 17th divisor bit was introduced to encode the multiples 135 * of 0.125 missing from the FT8U232AM. Bits 16 to 14 are coded as follows 136 * (the first four codes are the same as for the FT8U232AM, where bit 16 is 137 * always 0): 138 * 000 - add .000 to divisor 139 * 001 - add .500 to divisor 140 * 010 - add .250 to divisor 141 * 011 - add .125 to divisor 142 * 100 - add .375 to divisor 143 * 101 - add .625 to divisor 144 * 110 - add .750 to divisor 145 * 111 - add .875 to divisor 146 * Bits 15 to 0 of the 17-bit divisor are placed in the urb value. Bit 16 is 147 * placed in bit 0 of the urb index. 148 * 149 * Note that there are a couple of special cases to support the highest baud 150 * rates. If the calculated divisor value is 1, this needs to be replaced with 151 * 0. Additionally for the FT232BM, if the calculated divisor value is 0x4001 152 * (1.5), this needs to be replaced with 0x0001 (1) (but this divisor value is 153 * not supported by the FT8U232AM). 154 */ 155 156enum ftdi_chip_type { 157 SIO = 1, 158 FT8U232AM = 2, 159 FT232BM = 3, 160 FT2232C = 4, 161 FT232RL = 5, 162 FT2232H = 6, 163 FT4232H = 7, 164 FT232H = 8, 165 FTX = 9, 166}; 167 168enum ftdi_sio_baudrate { 169 ftdi_sio_b300 = 0, 170 ftdi_sio_b600 = 1, 171 ftdi_sio_b1200 = 2, 172 ftdi_sio_b2400 = 3, 173 ftdi_sio_b4800 = 4, 174 ftdi_sio_b9600 = 5, 175 ftdi_sio_b19200 = 6, 176 ftdi_sio_b38400 = 7, 177 ftdi_sio_b57600 = 8, 178 ftdi_sio_b115200 = 9 179}; 180 181/* 182 * The ftdi_8U232AM_xxMHz_byyy constants have been removed. The encoded divisor 183 * values are calculated internally. 184 */ 185#define FTDI_SIO_SET_DATA_REQUEST FTDI_SIO_SET_DATA 186#define FTDI_SIO_SET_DATA_REQUEST_TYPE 0x40 187#define FTDI_SIO_SET_DATA_PARITY_NONE (0x0 << 8) 188#define FTDI_SIO_SET_DATA_PARITY_ODD (0x1 << 8) 189#define FTDI_SIO_SET_DATA_PARITY_EVEN (0x2 << 8) 190#define FTDI_SIO_SET_DATA_PARITY_MARK (0x3 << 8) 191#define FTDI_SIO_SET_DATA_PARITY_SPACE (0x4 << 8) 192#define FTDI_SIO_SET_DATA_STOP_BITS_1 (0x0 << 11) 193#define FTDI_SIO_SET_DATA_STOP_BITS_15 (0x1 << 11) 194#define FTDI_SIO_SET_DATA_STOP_BITS_2 (0x2 << 11) 195#define FTDI_SIO_SET_BREAK (0x1 << 14) 196/* FTDI_SIO_SET_DATA */ 197 198/* 199 * BmRequestType: 0100 0000B 200 * bRequest: FTDI_SIO_SET_DATA 201 * wValue: Data characteristics (see below) 202 * wIndex: Port 203 * wLength: 0 204 * Data: No 205 * 206 * Data characteristics 207 * 208 * B0..7 Number of data bits 209 * B8..10 Parity 210 * 0 = None 211 * 1 = Odd 212 * 2 = Even 213 * 3 = Mark 214 * 4 = Space 215 * B11..13 Stop Bits 216 * 0 = 1 217 * 1 = 1.5 218 * 2 = 2 219 * B14 220 * 1 = TX ON (break) 221 * 0 = TX OFF (normal state) 222 * B15 Reserved 223 * 224 */ 225 226 227 228/* FTDI_SIO_MODEM_CTRL */ 229#define FTDI_SIO_SET_MODEM_CTRL_REQUEST_TYPE 0x40 230#define FTDI_SIO_SET_MODEM_CTRL_REQUEST FTDI_SIO_MODEM_CTRL 231 232/* 233 * BmRequestType: 0100 0000B 234 * bRequest: FTDI_SIO_MODEM_CTRL 235 * wValue: ControlValue (see below) 236 * wIndex: Port 237 * wLength: 0 238 * Data: None 239 * 240 * NOTE: If the device is in RTS/CTS flow control, the RTS set by this 241 * command will be IGNORED without an error being returned 242 * Also - you can not set DTR and RTS with one control message 243 */ 244 245#define FTDI_SIO_SET_DTR_MASK 0x1 246#define FTDI_SIO_SET_DTR_HIGH ((FTDI_SIO_SET_DTR_MASK << 8) | 1) 247#define FTDI_SIO_SET_DTR_LOW ((FTDI_SIO_SET_DTR_MASK << 8) | 0) 248#define FTDI_SIO_SET_RTS_MASK 0x2 249#define FTDI_SIO_SET_RTS_HIGH ((FTDI_SIO_SET_RTS_MASK << 8) | 2) 250#define FTDI_SIO_SET_RTS_LOW ((FTDI_SIO_SET_RTS_MASK << 8) | 0) 251 252/* 253 * ControlValue 254 * B0 DTR state 255 * 0 = reset 256 * 1 = set 257 * B1 RTS state 258 * 0 = reset 259 * 1 = set 260 * B2..7 Reserved 261 * B8 DTR state enable 262 * 0 = ignore 263 * 1 = use DTR state 264 * B9 RTS state enable 265 * 0 = ignore 266 * 1 = use RTS state 267 * B10..15 Reserved 268 */ 269 270/* FTDI_SIO_SET_FLOW_CTRL */ 271#define FTDI_SIO_SET_FLOW_CTRL_REQUEST_TYPE 0x40 272#define FTDI_SIO_SET_FLOW_CTRL_REQUEST FTDI_SIO_SET_FLOW_CTRL 273#define FTDI_SIO_DISABLE_FLOW_CTRL 0x0 274#define FTDI_SIO_RTS_CTS_HS (0x1 << 8) 275#define FTDI_SIO_DTR_DSR_HS (0x2 << 8) 276#define FTDI_SIO_XON_XOFF_HS (0x4 << 8) 277/* 278 * BmRequestType: 0100 0000b 279 * bRequest: FTDI_SIO_SET_FLOW_CTRL 280 * wValue: Xoff/Xon 281 * wIndex: Protocol/Port - hIndex is protocol / lIndex is port 282 * wLength: 0 283 * Data: None 284 * 285 * hIndex protocol is: 286 * B0 Output handshaking using RTS/CTS 287 * 0 = disabled 288 * 1 = enabled 289 * B1 Output handshaking using DTR/DSR 290 * 0 = disabled 291 * 1 = enabled 292 * B2 Xon/Xoff handshaking 293 * 0 = disabled 294 * 1 = enabled 295 * 296 * A value of zero in the hIndex field disables handshaking 297 * 298 * If Xon/Xoff handshaking is specified, the hValue field should contain the 299 * XOFF character and the lValue field contains the XON character. 300 */ 301 302/* 303 * FTDI_SIO_GET_LATENCY_TIMER 304 * 305 * Set the timeout interval. The FTDI collects data from the slave 306 * device, transmitting it to the host when either A) 62 bytes are 307 * received, or B) the timeout interval has elapsed and the buffer 308 * contains at least 1 byte. Setting this value to a small number 309 * can dramatically improve performance for applications which send 310 * small packets, since the default value is 16ms. 311 */ 312#define FTDI_SIO_GET_LATENCY_TIMER_REQUEST FTDI_SIO_GET_LATENCY_TIMER 313#define FTDI_SIO_GET_LATENCY_TIMER_REQUEST_TYPE 0xC0 314 315/* 316 * BmRequestType: 1100 0000b 317 * bRequest: FTDI_SIO_GET_LATENCY_TIMER 318 * wValue: 0 319 * wIndex: Port 320 * wLength: 0 321 * Data: latency (on return) 322 */ 323 324/* 325 * FTDI_SIO_SET_LATENCY_TIMER 326 * 327 * Set the timeout interval. The FTDI collects data from the slave 328 * device, transmitting it to the host when either A) 62 bytes are 329 * received, or B) the timeout interval has elapsed and the buffer 330 * contains at least 1 byte. Setting this value to a small number 331 * can dramatically improve performance for applications which send 332 * small packets, since the default value is 16ms. 333 */ 334#define FTDI_SIO_SET_LATENCY_TIMER_REQUEST FTDI_SIO_SET_LATENCY_TIMER 335#define FTDI_SIO_SET_LATENCY_TIMER_REQUEST_TYPE 0x40 336 337/* 338 * BmRequestType: 0100 0000b 339 * bRequest: FTDI_SIO_SET_LATENCY_TIMER 340 * wValue: Latency (milliseconds) 341 * wIndex: Port 342 * wLength: 0 343 * Data: None 344 * 345 * wValue: 346 * B0..7 Latency timer 347 * B8..15 0 348 * 349 */ 350 351/* 352 * FTDI_SIO_SET_EVENT_CHAR 353 * 354 * Set the special event character for the specified communications port. 355 * If the device sees this character it will immediately return the 356 * data read so far - rather than wait 40ms or until 62 bytes are read 357 * which is what normally happens. 358 */ 359 360 361#define FTDI_SIO_SET_EVENT_CHAR_REQUEST FTDI_SIO_SET_EVENT_CHAR 362#define FTDI_SIO_SET_EVENT_CHAR_REQUEST_TYPE 0x40 363 364 365/* 366 * BmRequestType: 0100 0000b 367 * bRequest: FTDI_SIO_SET_EVENT_CHAR 368 * wValue: EventChar 369 * wIndex: Port 370 * wLength: 0 371 * Data: None 372 * 373 * wValue: 374 * B0..7 Event Character 375 * B8 Event Character Processing 376 * 0 = disabled 377 * 1 = enabled 378 * B9..15 Reserved 379 * 380 */ 381 382/* FTDI_SIO_SET_ERROR_CHAR */ 383 384/* 385 * Set the parity error replacement character for the specified communications 386 * port 387 */ 388 389/* 390 * BmRequestType: 0100 0000b 391 * bRequest: FTDI_SIO_SET_EVENT_CHAR 392 * wValue: Error Char 393 * wIndex: Port 394 * wLength: 0 395 * Data: None 396 * 397 *Error Char 398 * B0..7 Error Character 399 * B8 Error Character Processing 400 * 0 = disabled 401 * 1 = enabled 402 * B9..15 Reserved 403 * 404 */ 405 406/* FTDI_SIO_GET_MODEM_STATUS */ 407/* Retrieve the current value of the modem status register */ 408 409#define FTDI_SIO_GET_MODEM_STATUS_REQUEST_TYPE 0xc0 410#define FTDI_SIO_GET_MODEM_STATUS_REQUEST FTDI_SIO_GET_MODEM_STATUS 411#define FTDI_SIO_CTS_MASK 0x10 412#define FTDI_SIO_DSR_MASK 0x20 413#define FTDI_SIO_RI_MASK 0x40 414#define FTDI_SIO_RLSD_MASK 0x80 415/* 416 * BmRequestType: 1100 0000b 417 * bRequest: FTDI_SIO_GET_MODEM_STATUS 418 * wValue: zero 419 * wIndex: Port 420 * wLength: 1 421 * Data: Status 422 * 423 * One byte of data is returned 424 * B0..3 0 425 * B4 CTS 426 * 0 = inactive 427 * 1 = active 428 * B5 DSR 429 * 0 = inactive 430 * 1 = active 431 * B6 Ring Indicator (RI) 432 * 0 = inactive 433 * 1 = active 434 * B7 Receive Line Signal Detect (RLSD) 435 * 0 = inactive 436 * 1 = active 437 */ 438 439/* FTDI_SIO_SET_BITMODE */ 440#define FTDI_SIO_SET_BITMODE_REQUEST_TYPE 0x40 441#define FTDI_SIO_SET_BITMODE_REQUEST FTDI_SIO_SET_BITMODE 442 443/* Possible bitmodes for FTDI_SIO_SET_BITMODE_REQUEST */ 444#define FTDI_SIO_BITMODE_RESET 0x00 445#define FTDI_SIO_BITMODE_CBUS 0x20 446 447/* FTDI_SIO_READ_PINS */ 448#define FTDI_SIO_READ_PINS_REQUEST_TYPE 0xc0 449#define FTDI_SIO_READ_PINS_REQUEST FTDI_SIO_READ_PINS 450 451/* 452 * FTDI_SIO_READ_EEPROM 453 * 454 * EEPROM format found in FTDI AN_201, "FT-X MTP memory Configuration", 455 * http://www.ftdichip.com/Support/Documents/AppNotes/AN_201_FT-X%20MTP%20Memory%20Configuration.pdf 456 */ 457#define FTDI_SIO_READ_EEPROM_REQUEST_TYPE 0xc0 458#define FTDI_SIO_READ_EEPROM_REQUEST FTDI_SIO_READ_EEPROM 459 460#define FTDI_FTX_CBUS_MUX_GPIO 0x8 461#define FTDI_FT232R_CBUS_MUX_GPIO 0xa 462 463 464/* Descriptors returned by the device 465 * 466 * Device Descriptor 467 * 468 * Offset Field Size Value Description 469 * 0 bLength 1 0x12 Size of descriptor in bytes 470 * 1 bDescriptorType 1 0x01 DEVICE Descriptor Type 471 * 2 bcdUSB 2 0x0110 USB Spec Release Number 472 * 4 bDeviceClass 1 0x00 Class Code 473 * 5 bDeviceSubClass 1 0x00 SubClass Code 474 * 6 bDeviceProtocol 1 0x00 Protocol Code 475 * 7 bMaxPacketSize0 1 0x08 Maximum packet size for endpoint 0 476 * 8 idVendor 2 0x0403 Vendor ID 477 * 10 idProduct 2 0x8372 Product ID (FTDI_SIO_PID) 478 * 12 bcdDevice 2 0x0001 Device release number 479 * 14 iManufacturer 1 0x01 Index of man. string desc 480 * 15 iProduct 1 0x02 Index of prod string desc 481 * 16 iSerialNumber 1 0x02 Index of serial nmr string desc 482 * 17 bNumConfigurations 1 0x01 Number of possible configurations 483 * 484 * Configuration Descriptor 485 * 486 * Offset Field Size Value 487 * 0 bLength 1 0x09 Size of descriptor in bytes 488 * 1 bDescriptorType 1 0x02 CONFIGURATION Descriptor Type 489 * 2 wTotalLength 2 0x0020 Total length of data 490 * 4 bNumInterfaces 1 0x01 Number of interfaces supported 491 * 5 bConfigurationValue 1 0x01 Argument for SetCOnfiguration() req 492 * 6 iConfiguration 1 0x02 Index of config string descriptor 493 * 7 bmAttributes 1 0x20 Config characteristics Remote Wakeup 494 * 8 MaxPower 1 0x1E Max power consumption 495 * 496 * Interface Descriptor 497 * 498 * Offset Field Size Value 499 * 0 bLength 1 0x09 Size of descriptor in bytes 500 * 1 bDescriptorType 1 0x04 INTERFACE Descriptor Type 501 * 2 bInterfaceNumber 1 0x00 Number of interface 502 * 3 bAlternateSetting 1 0x00 Value used to select alternate 503 * 4 bNumEndpoints 1 0x02 Number of endpoints 504 * 5 bInterfaceClass 1 0xFF Class Code 505 * 6 bInterfaceSubClass 1 0xFF Subclass Code 506 * 7 bInterfaceProtocol 1 0xFF Protocol Code 507 * 8 iInterface 1 0x02 Index of interface string description 508 * 509 * IN Endpoint Descriptor 510 * 511 * Offset Field Size Value 512 * 0 bLength 1 0x07 Size of descriptor in bytes 513 * 1 bDescriptorType 1 0x05 ENDPOINT descriptor type 514 * 2 bEndpointAddress 1 0x82 Address of endpoint 515 * 3 bmAttributes 1 0x02 Endpoint attributes - Bulk 516 * 4 bNumEndpoints 2 0x0040 maximum packet size 517 * 5 bInterval 1 0x00 Interval for polling endpoint 518 * 519 * OUT Endpoint Descriptor 520 * 521 * Offset Field Size Value 522 * 0 bLength 1 0x07 Size of descriptor in bytes 523 * 1 bDescriptorType 1 0x05 ENDPOINT descriptor type 524 * 2 bEndpointAddress 1 0x02 Address of endpoint 525 * 3 bmAttributes 1 0x02 Endpoint attributes - Bulk 526 * 4 bNumEndpoints 2 0x0040 maximum packet size 527 * 5 bInterval 1 0x00 Interval for polling endpoint 528 * 529 * DATA FORMAT 530 * 531 * IN Endpoint 532 * 533 * The device reserves the first two bytes of data on this endpoint to contain 534 * the current values of the modem and line status registers. In the absence of 535 * data, the device generates a message consisting of these two status bytes 536 * every 40 ms 537 * 538 * Byte 0: Modem Status 539 * 540 * Offset Description 541 * B0 Reserved - must be 1 542 * B1 Reserved - must be 0 543 * B2 Reserved - must be 0 544 * B3 Reserved - must be 0 545 * B4 Clear to Send (CTS) 546 * B5 Data Set Ready (DSR) 547 * B6 Ring Indicator (RI) 548 * B7 Receive Line Signal Detect (RLSD) 549 * 550 * Byte 1: Line Status 551 * 552 * Offset Description 553 * B0 Data Ready (DR) 554 * B1 Overrun Error (OE) 555 * B2 Parity Error (PE) 556 * B3 Framing Error (FE) 557 * B4 Break Interrupt (BI) 558 * B5 Transmitter Holding Register (THRE) 559 * B6 Transmitter Empty (TEMT) 560 * B7 Error in RCVR FIFO 561 * 562 */ 563#define FTDI_RS0_CTS (1 << 4) 564#define FTDI_RS0_DSR (1 << 5) 565#define FTDI_RS0_RI (1 << 6) 566#define FTDI_RS0_RLSD (1 << 7) 567 568#define FTDI_RS_DR 1 569#define FTDI_RS_OE (1<<1) 570#define FTDI_RS_PE (1<<2) 571#define FTDI_RS_FE (1<<3) 572#define FTDI_RS_BI (1<<4) 573#define FTDI_RS_THRE (1<<5) 574#define FTDI_RS_TEMT (1<<6) 575#define FTDI_RS_FIFO (1<<7) 576 577/* 578 * OUT Endpoint 579 * 580 * This device reserves the first bytes of data on this endpoint contain the 581 * length and port identifier of the message. For the FTDI USB Serial converter 582 * the port identifier is always 1. 583 * 584 * Byte 0: Line Status 585 * 586 * Offset Description 587 * B0 Reserved - must be 1 588 * B1 Reserved - must be 0 589 * B2..7 Length of message - (not including Byte 0) 590 * 591 */ 592