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CHAPTER 9: Theory of Operation & Board Layout

9.1 Theory of Operation

The heart of the 488 Controller is a 6809 microprocessor [U101] supported by 8K bytes of firmware EPROM
[U102 (2764)] and 32K bytes of static RAM [U103 (58256)]. A Versatile Interface Adapter [U104 (65B22)]
is used to generate real-time interrupts for the firmware operating system.

The front-panel annunciators are also driven by U104 through an inverter [U113 (74LS04)]. The IEEE
488 bus interface is accomplished by a TMS9914A [U106] controller with drivers U107 and U108. The
serial interface is provided by the UART [6551 (U105)]. If RS-232 levels are chosen, they are provided
by the RS-232 transceiver (U209). If RS-422 levels are selected, the differential driver [26LS30 (U207)]
and receiver [26LS33 (U208)] are used.

The internal DIP switches [SWl, SW2, and SW3] are read via 74HCT244 tri-state buffers [U201, U202, and
U203]. Power is supplied by an external unregulated 9-volt wallmount supply. Regulation to the required

+5 volts is provided by U206 [7805].

Decoding of the microprocessor address space is accomplished with a Programmable Logic Array [U110
(16L8)]. The Memory space allocation is:

Address

Device

Part Number

Function

$0000-$7FFF

U103

58258

Static RAM

$A000-$A007

U106

9914A

IEEE Controller

$A800-$A807

U105

6551

UART

$B000-$B00F

U104

65B22

VIA

$B800

U201

74HCT244

SW1 (S201)

$B801

U202

74HCT244

SW2 (S202)

$B802

U203

74HCT244

SW3 (S203)

$E000-$FFFF

U102

2764

Programmed EPROM

9. Theory of Operation & Board Layout

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Summary of Contents for 488 Controller

Page 1: ...1000 Park Drive Lawrence PA 15055 1018 724 746 5500 Fax 724 746 0746 Copyright 2007 Black Box Corporation All rights reserved...

Page 2: ...technical support 24 hours a day 7 days a week Call 724 746 5500 or fax 724 746 0746 Mailing address Black Box Corporation 1000 Park Drive Lawrence PA 15055 1018 Web site www blackbox com E mail info...

Page 3: ...s operated in a commercial environment Operation of this equipment in a residential area is likely to cause interference in which case the user at his own expense will be required to take whatever mea...

Page 4: ...ire por los orificios de ventilaci n 10 El equipo el ctrico deber ser situado fuera del alcance de fuentes de calor como radiadores registros de calor estufas u otros aparatos incluyendo amplificadore...

Page 5: ...d equipment before internal access to the device is permitted An external power supply is provided with this product Its input is 100 240 VAC 50 60 Hz 0 5 A maximum power draw Its 9 VDC 15 W maximum 1...

Page 6: ...BOX and the Double Diamond logo are registered trademarks of BB Technologies Inc Hewlett Packard and HP are registered trademarks of Hewlett Packard AT and IBM are registered trademarks of IBM Corpor...

Page 7: ...hru Features 21 3 6 2 Peripheral Pass Thru Features 22 3 7 Serial Interface 22 3 7 1 RS 232 RS 422 Signal Level Selection 22 3 7 2 Serial Signal Descriptions 23 3 7 3 Serial Cable Wiring Diagrams 24 3...

Page 8: ...isten Address MLA 83 7 6 3 Device Clear DCL and SDC 84 7 6 4 Interface Clear IFC 84 7 6 5 Serial Poll Enable SPE 84 7 6 6 Serial Poll Disable SPD 84 7 6 7 Unlisten UNL 84 7 6 8 Untalk UNT 84 7 7 IEEE...

Page 9: ...G 90 8 7 14 Parallel Poll Configure PPC 90 8 7 15 Parallel Poll Unconfigure PPU 90 8 8 More On Service Requests 90 8 8 1 Serial Poll 90 8 8 2 Parallel Poll 90 9 Theory of Operation Board Layout 91 9 1...

Page 10: ...TxD and RxD Character Set Asynchronous bit serial Output Voltage 5 volts minimum RS 232C 3 5 volts typical RS 422A Input Voltage 3 volts minimum 15 volts maximum Baud Rate Selectable 110 300 600 1200...

Page 11: ...ification FCC CE Indicators 4 LEDs Talk Listen SRQ Error and Power Power Input 100 240 VAC autosensing 50 60 Hz 0 5 A maximum Output 9 V 15 W maximum 1 7 A Size 2 7 H x 5 5 W x 7 4 D 6 9 x 14 x 18 8 c...

Page 12: ...nd protocol are similar to those used by the Hewlett Packard HP 85 computer Additional features provide a transparent IEEE to serial converter and a serial to IEEE pass thru controller As a serial to...

Page 13: ...xecute Trigger GTL Go To Local LA Listener Active LAG Listen Address Group LF Line Feed LLO Local Lock Out MLA My Listen Address MTA My Talk Address PE Peripheral PPC Parallel Poll Configure PPU Paral...

Page 14: ...elow and on the next page illustrate the factory default conditions which are Serial Port IEEE 9600 Baud Mode System Controller 8 Data Bits Address 10 2 Stop Bits Bus Terminator CR LF EOI Disabled No...

Page 15: ...W1 factory default settings 1 2 3 4 5 6 7 8 OPEN SW1 Baud Rate Handshake Word Length 9600 RTS CTS 8 Data Bits Switch Side View DOT Pass Thru Feature Enabled Stop Bits 2 Stop Bits 1 2 3 4 5 6 7 8 OPEN...

Page 16: ...l cables prior to disassembly WARNING Never open the 488 Controller s case while it is connected to the AC line Failure to observe this warning may result in equipment failure personal injury or death...

Page 17: ...TS SW1 6 determines the number of data bits often referred to as word length for each serial character transmitted or received The factory default is 8 data bits Figure 3 5 Switch SW1 Selecting the se...

Page 18: ...S2 8 The 488 Controller generates the selected parity during serial transmissions but it does not check parity on data that is received The factory default is parity disabled Figure 3 7 Switch SW2 Sel...

Page 19: ...m the serial host it is communicating with RTS CTS serial control becomes inactive when X ON X OFF is enabled The RTS output is however set to an active high state The CTS input is not used for this h...

Page 20: ...put terminator to an IEEE controller which expects a carriage return followed by a line feed CR LF In the above case the serial terminator should be selected for CR Only while the IEEE terminator is s...

Page 21: ...inator is sent Factory default is CR LF with EOI disabled Figure 3 11 Switch SW3 Selecting the IEEE bus terminator 3 4 Selecting the Mode SW2 1 and SW2 2 set the major operating mode of the 488 Contro...

Page 22: ...ed by the 488 Controller until it is read by the IEEE controller Refer to Chapter 7 for more detailed information on the Peripheral Pass Thru operation mode The factory default is the System Controlle...

Page 23: ...TURES In the IEEE Controller RS 232 to IEEE 488 converter mode SW1 7 determines whether the interface should after sending the IEEE bus terminators address the attached bus device to talk The factory...

Page 24: ...If the interface is to be connected to an IBM PC or compatible select the RS 232 level If it will be connected to a Macintosh use the RS 422 level For connection to other computers refer to the manuf...

Page 25: ...ue CTS Clear To Send Input Pin 4 The CTS input is used as a hardware handshake line to prevent the 488 Controller from transmitting serial data when the RS 232 host is not ready to accept it When RTS...

Page 26: ...itches The signal level is high true and only connected to this pin when RS 422 operation is selected It is 180 degrees out of phase with RxD TxD Transmit Data Plus Output Pin 16 This pin transmits se...

Page 27: ...S 232 Figure 3 20 Wiring diagram IBM AT or compatible with DB9 serial connector to 488 Controller RS 232 NOTE Standard AT 9 pin to 25 pin adapter cables are not wired as shown above and will not work...

Page 28: ...end of this self check all indicators except POWER should turn off If there is an error in the ROM checksum all of the LEDs will remain on Flashing LEDs indicate a RAM failure Should such an error oc...

Page 29: ...equivalent OPEN COM1 9600 N 8 2 cd ds AS 1 Return PRINT 1 HELLO Return LINE INPUT 1 A Return PRINT A Return The 488 Controller will respond with and the host will display 488 Controller Revision N N C...

Page 30: ...stem Controller remains the System Controller The device to which control is passed must be able to take on the Active Controller role It would make no sense to try to pass control to a printer Contro...

Page 31: ...ain control by asserting Interface Clear or by receiving control A Peripheral can become the Active Controller by receiving control and can give up control by Passing Control or upon detecting Interfa...

Page 32: ...LOCAL Unassert Remote Enable or send Go To Local to selected devices REMOTE Assert Remote Enable optionally setting devices to Remote LOCAL LOCKOUT Prevent local front panel control of bus devices CL...

Page 33: ...listen in preparation for sending data There are two ways to detect our being addressed to listen through the STATUS command or by detecting an event with the ARM or ON DOMACRO commands The STATUS 1...

Page 34: ...F STATE L THEN 400 290 Are we addressed to talk 300 IF STATE T THEN 500 310 PRINT BAD ADDRESSED STATE VALUE ST STOP This means are we still in a state where there is no communication If we are address...

Page 35: ...can ENTER from the bus IDLE The 488 Controller is in neither the Talk nor Listen state CHANGE An Address Change has occurred i e a change between Peripheral and Controller or among Talk Listen and Idl...

Page 36: ...bus device or check the Service Request state PPOLL Parallel Poll the bus PPOLL CONFIG Configure Parallel Poll responses PPOLL DISABLE Disable the selected bus devices Parallel Poll response PPOLL UN...

Page 37: ...municate with the IEEE 488 bus System commands configure or request information from the 488 Controller Bus Commands ABORT PPOLL CONFIG CLEAR PPOLL DISABLE ENTER PPOLL UNCONFIG LOCAL REMOTE LOCAL LOCK...

Page 38: ...g the ID command The number sign and the semicolon must be present exactly as shown A comma represents an address separator You can use the slash or period in its place as the address separator Use op...

Page 39: ...Character Count count The number of characters to be transferred A pound sign followed by an integer in the range of 1 to 65535 216 1 May be specified in hexadecimal by preceding it with H The hexadec...

Page 40: ...serial host s COM port after sending the command If a response is provided it must be read to maintain proper program sequence 5 2 3 MODE This command description section specifies the operating modes...

Page 41: ...PPC Parallel Poll Configure x 0 0 0 0 1 0 1 PPD Parallel Poll Disable x 1 1 1 0 0 0 0 PPE Parallel Poll Enable x 1 1 0 S P3 P2 P1 PPU Parallel Poll Unconfigure x 0 0 1 0 1 0 1 REN Remote Enable SDC S...

Page 42: ...n the serial input buffer requests one of the last 10 queues 1270 character locations left it signals the serial host that it should stop sending data This is accomplished by either unasserting RTS or...

Page 43: ...fer commands If X ON X OFF handshake is selected the software handshake state is reset The character referred to as the ID character can be changed or disabled by using the ID command If you anticipat...

Page 44: ...e event message SRQ is returned to the serial host when the state of the Service Request Bus Line is detected in the asserted state This event is level sensitive If the condition exists at the time th...

Page 45: ...ller with either an UNT or UNL command This event is edge sensitive When the event message is sent the internal address change status as read by the STATUS 1 command is cleared This event is tested be...

Page 46: ...vent event where event may include Event Abbreviated Form SRQ SRQ PERIPHERAL PE CONTROLLER CO TRIGGER TR CLEAR CL TALK T LISTEN L IDLE I CHANGE CH ERROR ER If no event is specified ARM SRQ is assumed...

Page 47: ...NSE None MODE CA BUS STATES ATNDCL all devices ATNUNL MTA LAG SDC selected devices EXAMPLES PRINT 1 CLEAR Issue a Device Clear to all devices PRINT 1 CL 12 18 Issue a Selected Device Clear to devices...

Page 48: ...ENT Command The COMMENT command is provided to allow the user to place comment lines in a macro buffer The COMMENT string is enclosed in either apostrophes or quotation marks When the macro is execute...

Page 49: ...s the 488 Controller from sending the event s status message to the serial host even when the specified conditions occur It is also used to disable the ON event DOMACRO response The user s program can...

Page 50: ...ecified the 488 Controller must already be configured to receive data either as a result of an immediately preceding ENTER command or as a result of a SEND sub command A timeout error will occur if en...

Page 51: ...nd receives data from the bus under Active Controller s control The Active Controller must put the 488 Controller into the Listen state and configure some bus device to provide the 488 Controller with...

Page 52: ...pecified then count characters will be returned followed by the serial output terminators Otherwise the response ends when the IEEE bus input terminator is detected and the serial output terminators a...

Page 53: ...AMPLES PRINT 1 ERASE Erase all macro buffers PRINT 1 ERASE 20 Erase macro buffer 20 ERROR Command The ERROR command enables or disables automatic reporting of the 488 Controller error messages on comm...

Page 54: ...double ID character command the ID character will default back to The desired character must immediately follow the semicolon without intervening spaces The and command can be disabled by not includin...

Page 55: ...L or LO RESPONSE None MODE SC BUS STATES REM EXAMPLE PRINT 1 LOCAL Unassert the REN Line SYNTAX LOCAL addr addr or LO addr addr addr is a bus device address RESPONSE None MODE CA BUS STATES ATNUNL MTA...

Page 56: ...low You should refer to the command description for complete information COMMENT The COMMENT command allows the user to send a predefined ASCII string to the serial host when the macro is executed COU...

Page 57: ...10 8 Execute it 8 more times 140 FOR N 1 TO 8 Read data 8 times 150 INPUT 1 M PRINT M Read Comment Memory 160 INPUT 1 R PRINT R Read data from ENTER16 170 INPUT 1 R PRINT R Read data from ENTER10 180...

Page 58: ...mmand There are two types of events level sensitive and edge sensitive Level sensitive events such as SRQ will cause macro execution every time they are enabled while the event condition persists Usua...

Page 59: ...his event is edge sensitive IDLE This event occurs when the 488 Controller as a Peripheral CA transitions from a Talker or Listener state to a idle state neither talker or listener It indicates that t...

Page 60: ...R CL TALK T LISTEN L IDLE I CHANGE CH ERROR ER RESPONSE None MODE any BUS STATES None EXAMPLE 10 PRINT 1 MACRO 0 Create Macro 0 20 PRINT 1 COMMENT I have received an SRQ 30 PRINT 1 ENDM 40 PRINT 1 ON...

Page 61: ...om the serial input The serial input terminator s are replaced with the bus output terminator s before being sent to the bus devices The number of characters that can be set to a bus device is limited...

Page 62: ...he IEEE bus output terminators can be modified with the TERM command Refer to the description of the TERM command for complete information Even as a Peripheral the 488 Controller might be the System C...

Page 63: ...t IEEE bus data lines DIO1 through DIO8 with DIO1 being the least significant In this manner up to eight devices may simultaneously be polled by the controller More than one device can share any parti...

Page 64: ...hen its ist is a logical 0 i e it does not require attention However the meaning of ist can vary between devices so refer to your IEEE bus device documentation The remaining 3 least significant bits o...

Page 65: ...The READ command is used to inspect the contents of a defined macro buffer Macro buffers can be individually specified by their number When a READ command is received a copy of the macro buffer reques...

Page 66: ...8 Controller REQUEST takes a numeric argument in the range of 0 to 255 H0 to HFF that is used to set the Serial Poll status When the 488 Controller is Serial Polled by the Controller it returns this b...

Page 67: ...following commands ABORT If System Controller DISARM ERASE ERROR OFF LOCAL If System Controller REQUEST 0 With rsv cleared if peripheral TIME OUT 0 TRACE OFF Clear CHANGE TRIGGER and CLEAR STATUS The...

Page 68: ...command ATN is asserted MTA Send My the 488 Controller s Talk Address ATN is asserted MLA Send My the 488 Controller s Listen Address ATN is asserted TALK addr Send Talk Address addr device TAG ATN is...

Page 69: ...tion of a Line Feed LF character Note that the maximum length of the SEND command including any subcommands is 127 characters If large amounts of data must be transferred using the SEND command then m...

Page 70: ...a 64 If it is not asserted the 488 Controller will return a 0 In Peripheral mode the SPOLL command is issued without an address and returns 488 Controller s own serial poll status If rsv DIO7 decimal...

Page 71: ...essage is sent by the 488 Controller the error condition is cleared Refer to Appendix B for explanations of error messages The 488 Controller also includes an extended status command STATUS 1 The STAT...

Page 72: ...data transfer can be determined The Service Request indicator reflects the external SRQ status If the SRQ line is asserted S1 will be reported If it is unasserted S0 will be reported The Error Code i...

Page 73: ...ating condition It strips all CR and LF from the input data and appends the serial output terminator s before sending it to the serial host The default serial terminators for output are set by interna...

Page 74: ...ave been received During output EOI specifies that the EOI bus signal is to be asserted during the last byte transferred SYNTAX TERM term term EOI EOI NONE or TE term term EOI EOI NONE term is one of...

Page 75: ...ro commands during macro execution MODE Any BUS STATES None EXAMPLES PRINT 1 TRACR ON Enable Tracing PRINT 1 DOMACRO 0 Execute and trace macro 0 TRIGGER Command The TRIGGER command issues a Group Exec...

Page 76: ...talk it uses the following bus sequence ATNUNL MLA TAG ATN The 488 Controller then accepts data from the IEEE device and returns it to the host until the last selected IEEE terminator is detected The...

Page 77: ...re shows the IEEE address selection of 10 Figure 6 1 SW3 view for IEEE address selection 6 4 Talk Back On Terminator A switch selectable talk back feature is included to provide bidirectional communic...

Page 78: ...mmunications port 60 OPEN COM1 9600 N 8 2 AS 1 70 Set the Model 196 DMM to the 30 VDC range 80 PRINT l F0R3X The suppresses terminators 90 Request 10 Readings from 196 100 FOR N 1 to 10 110 PRINT l Ou...

Page 79: ...6 Figure 6 3 Selecting RS 232 signal levels After configuration turn on the plotter and the 488 Controller The 488 Controller s front panel LEDs should all light momentarily while it performs an inter...

Page 80: ...such as printers or plotters Refer to the printer s instruction manual if there is a question as to whether the printer requires secondary commands Figure 6 4 488 Controller settings for use with an H...

Page 81: ...e mini buffer or queue When the serial input or IEEE input requires more buffer space additional queues are allocated When a queue is empty it is released from the input buffers so that it may be re a...

Page 82: ...10 bytes per second The IEEE bus controller is capable of sending data to the 488 Controller at a rate of 5000 bytes per second The data would be transferred on the bus at 5000 characters per second f...

Page 83: ...set to a logical 1 when there are 1280 or fewer locations in the buffer for data It is cleared set to a logical 0 when there are more than 1280 locations available This bit is referred to as the IEEE...

Page 84: ...ne or more data bytes which have not been sent out the IEEE bus It is cleared set to 0 when the buffer is empty DIO4 IEEE Input Buffer Full When this bit is set it indicates that the 488 Controller ma...

Page 85: ...th the serial and IEEE terminators to be CR Only or LF Only To decide which terminators are appropriate see the instruction manuals for the serial device and the IEEE controller For selection of the 4...

Page 86: ...oll response until it is Serial Poll Disabled by the controller 7 6 6 SERIAL POLL DISABLE SPD Disables the 488 Controller from responding to serial polls by the controller 7 6 7 UNLISTEN UNL UNL place...

Page 87: ...k is the Active Talker There can only be one Talker at a time if the information transferred is to be clearly understood by all The act of giving the floor to that device is called Addressing to Talk...

Page 88: ...by addressing those devices to listen d Indicate to all devices that the data transfer can take place Figure 8 1 IEEE 488 bus structure Device 1 System Controller Able to Talk Listen and Control Devi...

Page 89: ...ation contained on the data lines is to be interpreted as a multiline command If it is not then that information is to be interpreted as data for the Active Listeners The Active Controller is the only...

Page 90: ...state the Talker asserts DAV active low to indicate that the data on the bus is valid 8 5 2 NOT READY FOR DATA NRFD This line is used by the Listeners to inform the Talker when they are ready to acce...

Page 91: ...th this group The 3 most significant bits of the data bus are set to 010 while the 5 least significant bits are the address of the device being told to talk 8 7 5 UNTALK UNT This command tells bus dev...

Page 92: ...he Controller says Do what I told you to do and let me know when you re done or Tell me when something is wrong Since SRQ is a single line command there is no way for the Controller to determine which...

Page 93: ...provided by the RS 232 transceiver U209 If RS 422 levels are selected the differential driver 26LS30 U207 and receiver 26LS33 U208 are used The internal DIP switches SWl SW2 and SW3 are read via 74HCT...

Page 94: ...488 CONTROLLER 92 9 2 Board Layout Figure 9 1 The 488 Controller s motherboard...

Page 95: ...93 CHAPTER 9 Theory of Operation Board Layout Figure 9 2 The interface converter s serial I O board...

Page 96: ...xecuted DELAY DELAY time Waits until time in seconds has elapsed before continuing DISARM DI SARM event event Disables transmission of event messages and ON event DOMACRO actions DOMACRO DO MACRO numb...

Page 97: ...arallel Poll response of a bus device Response is the decimal equivalent of four bits S P2 P1 P0 PPOLL DISABLE PPOLL D ISABLE addr addr or PPD addr addr Prevent bus device s from responding to a Paral...

Page 98: ...ial output terminator TERM TE RM term term EOI EOI NONE Set the serial output terminator TIME OUT TI ME OUT time Set the number of time in seconds to wait for a bus transfer before a timeout error wil...

Page 99: ...served 06 NO MACRO A DOMACRO or READ command was received but the Macro buffer specified is empty 07 MACRO OVERFLOW No memory is available to allocate as a Macro buffer 08 COMMAND OVERFLOW More than 1...

Page 100: ...by an external device 15 TIMEOUT READ The specified TIME OUT time has elapsed while the 488 Controller was waiting for a data byte from an external device 16 OUT OF MEMORY The 488 Controller was unab...

Page 101: ...0 t 74 SCG 116 NAK 15 PPU 21 25 05 37 5 35 21 53 E 45 05 69 U 55 21 85 e 65 SCG 101 u 75 SCG 117 SYN 16 22 26 06 38 6 36 22 54 F 46 06 70 V 56 22 86 f 66 SCG 102 v 76 SCG 118 ETB 17 23 27 07 39 7 37 2...

Page 102: ...488 CONTROLLER 100 How To Read the Chart Hexadecimal Decimal Equivalent Equivalent ASCII Character Address or Command...

Page 103: ...50 REM The 488 Controller must be configured as the System Controller 60 REM 70 REM 80 REM 90 REM 100 CLS 110 Open the serial communications port and set parameters 120 OPEN COM1 9600 n 8 2 cs ds AS...

Page 104: ...S 50 Open the serial communications port and set parameters 60 OPEN COM1 9600 N 8 2 cs ds AS 1 70 X ON LOOP 80 K INKEY PRINT 1 K PRINT K 90 WHILE NOT EOF 1 100 PRINT INPUT 1 1 110 IF LOC 1 70 THEN PRI...

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