Odd Crc | SMC Networks SMC91C95 manual

BYTE COUNT - Divided by two, it defines the total number of words including the STATUS WORD, the BYTE COUNT WORD, the DATA AREA and the CONTROL BYTE.

The receive byte count always appears as even; the ODDFRM bit of the receive status word indicates if the low byte of the last word is relevant.

The transmit byte count least significant bit will be assumed 0 by the controller regardless of the value written in memory.

DATA AREA - The data area starts at offset 4 of the packet structure and can extend up to 1536 bytes.

The data area contains six bytes of DESTINATION ADDRESS followed by six bytes of SOURCE ADDRESS, followed by a variable-length number of bytes. On transmit, all bytes are provided by the CPU, including the source address. The SMC91C95 does not insert its own source address. On receive, all bytes are provided by the CSMA side.

The 802.3 Frame Length word (Frame Type in Ethernet) is not interpreted by the SMC91C95. It is treated transparently as data both for transmit and receive operations.

CONTROL BYTE - The CONTROL BYTE always resides on the high byte of the last word. For transmit packets the CONTROL BYTE is written by the CPU as:

X

X

ODD

CRC

0

0

0

0

ODD - If set, indicates an odd number of bytes, with the last byte being right before the CONTROL BYTE. If clear, the number of data bytes is even and the byte before the CONTROL BYTE is not transmitted.

CRC - When set, CRC will be appended to the frame. This bit has only meaning if the NOCRC bit in the TCR is set.

For receive packets the CONTROL BYTE is written by the controller as:

0

1

ODD

0

0

0

0

0

ODD - If set, indicates an odd number of bytes, with the last byte being right before the CONTROL BYTE. If clear, the number of data bytes is even

and the byte before the CONTROL BYTE should be ignored.

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Image 30

SMC Networks SMC91C95 manual Odd Crc, Byte before the Control Byte should be ignored

Contents

Features Bus Interface Table of Contents PIN Configuration Network InterfaceSoftware Drivers General Description OverviewPage Uses non-volatile jumperless setup via serial Eeprom ISAPcmcia Function ISA Pcmcia Number Pins PIN Requirements Recp Crystal OSC XTAL1 XTAL2 Power VDD Avdd Ground GNDTotal Pins Coln PIN no Name Symbol Type Description Description of PIN Functions Enable Select card on odd byte accesses Ready ISA Byte High Enable input. Asserted lowPcmcia Card Enable 2 input. Used to Reset Value of INT SEL1-0 bits in the Configuration Application of the VCC or Reset which everISA Output. Active high interrupt signal. Register. This interrupt is tri-stated when not Is with Input. Active low read strobe used to access Whenever the SMC91C95 is in 16 bit modeEnable Function bit in the Ecor Interrupt pin if enabled Value of the Mringin input. When entering Pin is active high when either the PwrdwnOutput B Powerdown mode Pwrdwn bit is zero Pin when enabled by the Audio bit Modem Eeprom Eedo Eeprom EeskEeprom Eecs Sdout Eeprom Register RxclkTXD AUI Tperxn TPE Tpetxp TPE TpetxdpTxclk Avss EndecVSS Buffer Types SMC91C95 SMC91C95 SMC91C95 Internal Block Diagram Bus Transactions in ISA Mode NSBHE D0-D7 D8-D15 BIT ModeFunctional Description No Cycle Bus Transactions in Pcmcia Mode NCE1 NCE2 D0-D7 D8-D15Even byte IOis8=1 + nEN16=1.16BIT=0 Even byte Signals ISA Pcmci ON-CHIP Depth Width Used SMC91C95 Address SpacesROM Buffer Memory Mapping and Paging VS. Receive and TX Area CPU Side TX Fifo TX CompletionFifo Receive Queue and Mapping Internal Block DiagramSMC91C95 With Packet Format in Buffer Memory Transmit Packet Receive Packet ODD CRC ODDByte before the Control Byte should be ignored Receive Frame Status Word Address Hash Value Multicast Table BIT Interrupt Structure Function Pcmcia Mode ISA ModeInterrupt Output NIREQ when either function is SMC91C95 Interrupt Merging Ecor Reset LogicReset Functions Mcor Powerdown Powers Does not Entered Exited Power Down Powerdown LogicPowerdown Functions Pwrdwn Pcmcia Configuration Registers Address 8000-803Eh Pcmcia Attribute Memory Address 0- 7FFEh Attribute Memory Address Using Serial Eeprom 7FFEh 8000h 803Eh Space ISA and Pcmcia ModeTypesymbol Offsetname Internal I/O Space Mapping BANK0 BANK1 BANK2 BANK3 BANK4 BANK5 BS0 Bank Select Register Offset Name Type Symbol READ/WRITE BSRHigh Byte LOW BS2 BS2 BS1 BS0 BANK# High Fdse EPH STP Fdupl MON Nocrc Byte Loop Sqet LOW Pade Forco Loop Txena Byte Transmits AUI Fdse Fduplx Ephloop Loop Loops AT Network Carr LOW LTX Sqet High Link CTR EXC Lost Latcol Wakeu ByteOvrn LTX MULPage LOW Almul Prms Byte Abort High SoftStrip Rxen Byte RST CAR Rxabort RxovrnintPage Memory Size Actual Memory Register FFH Register READ/WRITE Space BANK0 Offset Name Type Symbol Memory ConfigurationMCR Device DIS High Full SET AUI Byte Wait StepSelec INT Byte INT SEL1 INT SEL0 Interrupt PIN Used RA17 A15 A14 A13Byte LOW ROM Size RA15 RA14 High Address Byte LOW High Byte LOW Byte High Data Byte LOW Data Byte Release LOW Eeprom Reload Store Byte Enable High RCVWakeu Auto Byte BAD Pcmcia Eeprom to Sram Memory Map 3FD 3FA3FC 3FF Busy Bit Readable High Byte LOW Command N0/BUSCommand SET xyz 000 0 Noop no Operation Command Sequencing This register is updated upon an Allocate Memory MMU command Failed Allocated Packet NumberPage Page Space BANK2 Offset Name Type Symbol Through AhData Register READ/WRITE Data High Data LOW Ercv EPH INT Rxovr Alloc TX INT RCV INT Empty Ercv INT Rxovr Empty TX INTPage INT LOW Multicast Table Byte High MDOE=0 MDOE=1 NXNDEIOS2 IOS1 IOS0 Byte LOW Mdoe Mclk MDI MDO Bit MDO High Byte LOW Byte Chip REV Chip ID Value Device High Byte LOW RCV Byte Discr Theory of Operation Memory ArchitectureFull Duplex Ethernet Support Behavior in Fdse Mode Main 802.3 section affected by Fdse is Typical Flow of Events for Transmit Driver CSMA/CD Side Typical Flow of Events for Receive Driver CSMA/CD Side Ethernet Interrupt Service Routine CSMA/CD MMU RAM RX Intr TX Intr Assumes Auto Release Option Selected Txempty Intr Driver Send and Allocate Routines Memory Partitioning Interrupt Generation Internal VS. External Attribute Memory MAP Attribute Memory Decodes Using Serial Eprom Wrattri Pcmcia Configuration Registers DescriptionSreset Ireq 8002h Ethernet Configuration and Status Register Ecsr IOIs8Page LevIREQ Enable Pcmcia functionality, this bit must be set IOIs8 Reserved Audio 8024h Pin Replacement Register PRR Current Value Value Written NEW Value Ringevent Ringenable 8028h Extended Status RegisterESR 802Ah Modem I/O Base Register 802Ch Modem I/O Base Register A15 A14 A13 A12 A11 A10 8032h Modem I/O Size Register Functional Description of the Blocks Memory Management UnitArbiter BUS Interface Wait State Policy DMA Block Packet Number Fifos DMA MMU Packet Number Flow and Relevant Registers Csma Block AUI Network Interface10BASE-T Physical Interface Transmit Functions Receive Functions Page Eeprom Word Board Setup Information ISA ModeEthernet Individual Address I/O Base Address Register Address Diagnostic LEDs Arbitration ConsiderationsPage 64 X 16 Serial Eeprom MAP for ISA Mode 103 Maximum Guaranteed Ratings Operational DescriptionParameter Symbo MIN TYP MAX Units Comments ID Type Buffers Input LeakageIP Type Buffers Type Buffer OD24 Type Buffer OD16 Type BufferOD162 Type Buffer Limits Parameter Symbo MIN TYP MAX Unit Test Condition Parameter MIN TYP MAX Units Capacitive Load on OutputsINTRO-INTR3 Data Valid Timing DiagramsA50, nREG NCE1 NOE D150 30 max Max Min 108 Address/nREG Setup Time to NWE Low NWE High NCE1 Low to nWE High Setup109 O Read Timing Table on the following 110 Parameter Min Typ Max Units O Write Timing Table on the following 112 100 Card Configuration Registers READ/WRITE Pcmcia Mode A15=1 114 NINPAC 115 Consecutive Pcmcia Write Cycles 116 Pcmcia Attribute Memory READ/WRITE A15=0 117 Mringoutb 118 ISA Consecutive Read Cycles 119 ISA Consecutive Write Cycles 120 ISA Consecutive Read and Write Cycles 121 Data Register Special Read Access 122 Data Register Special Write Access 123 BIT Mode Register Cycles 124 ISA Register Access When Using Bale 125 External ROM Read Access Using Bale 126 Eeprom Read 127 Eeprom Write 128 Memory Read Timing 129 External Endec Interface Start of Transmit 130 Differential Output Signal Timing 10BASE-T and AUI 131 Recp Recn Tperxpn Tperxp Tperxn Recp Recn Transmit Timing END of Frame AUI and 10BASE-T 134 Collision Timing AUI 135 Vtqfp Package Outline 136Page Kennedy Drive Hauppauge, NY 516 435-6000 FAX 516