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NorthStar HSIO-4 User's & Technical Manual

Horizon serial input/output four port
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N orttiSlar^
HSIO-4
HORIZON
Serial In p u t/O u tp u t-
Four Port
USER/TECHNICAL MANUAL

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Summary of Contents for NorthStar HSIO-4

  • Page 1 N orttiSlar^ HSIO-4 HORIZON Serial In p u t/O u tp u t- Four Port USER/TECHNICAL MANUAL...
  • Page 2 NorfhSta^ North Star Computers, Inc. 14440 C atalina St.. San Leandro, CA 94577 USA (415) 357-8500 TWX/Telex (91 0 ) 366-7001 HSIO-4 HORIZON Serial Input/Output — Four Port USER/TECHNICAL MANUAL HORIZON® is a registered trademark of North Star Computers, Inc.

  • Page 3: Table Of Contents

    TABLE OF CONTENTS SECTION 1 GENERAL INFORMATION PAGE 1.1 Introduction 1.2 Warranty 1.3 Features of the HSIO-4 SECTION 2 INSTALLING THE HSIO-4 2.1 Unpacking the HSIO-4 2.2 Setting I/O Address Switches for the North Star TSS/A 2.3 Configuration Changes 2.4 Completing Installation...
  • Page 4 PAGE 3.3 Synchronous Operation 3.3.1 Fixed Baud Rate of 55.8KHz A. Configuring Port as Modem B. Configuring Port as Terminal 3.3.2 Programmable Baud Rates A. Configuring Port as Modem B. Configuring Port as Terminal 3.3.3 Programming Baud Rates 3.3.4 Alternative Baud Rates 3.3.5 Sample Program 3.4 Interrupts 3.4.1 Arming and Disarming Maskable...
  • Page 5 5.1.3 Configuring Basic for Auto-Start Operation 5.2 Software Testing 5.3 Oscilloscope Testing 5.4 Repair Procedures APPENDICES A. RS-232 Connector Pin Assignments B. Notes On The Interface To The USART and USART Manufacturer Specification C. HSIO-4 Parts List D. Schematic Drawings...

  • Page 6: General Information

    S-100 bus systems. This manual provides basic instructions on how to install the HSIO-4 board in your HORIZON; it also provides technical information and detailed instructions for implementing a range of HSIO-4 features and operating characteristics.

  • Page 7: Warranty

    There are no warranties which extend beyond those expressly stated herein. This limited warranty is made in lieu of all other warranties, expressed or implied, and is limited to repair or replacement of the product. North Star HSIO-4 User/Technical Manual...

  • Page 8: Features Of The Hsio-4

    FEATURES OF THE HSIO-4 The HSIO-4 is a 4-port serial input/output board designed by North Star Computers, Inc., for use with the HORIZON and North Star multi-user systems. As supplied, the HSIO-4 is configured for use with the North Star TSS/A Multi-User System for Application Software.

  • Page 9: Installing The Hsio-4

    SECTION 2 INSTALLING THE HSIO-4 UNPACKING THE HSIO-4 The HSIO-4 board is shipped in a carton containing: North Star HSIO-4 board Four ribbon cables Plastic envelope containing eight jackscrews, lockwashers, and nuts. HSIO-4 User/Technical Manual Examine the contents of the carton to make sure they match this list.

  • Page 10: Setting I/O Address Switches For The North Star Tss/A

    SETTING I/O ADDRESS SWITCHES FOR THE NORTH STAR TSS/A As supplied, the I/O address switches on the HSIO-4 board are set for use with the North Star TSS/A (Multi-User System for Application Software). The I/O addresses for each port are set by the four switches located in the upper right corner of the board.

  • Page 11: Configuration Changes

    CONFIGURATION CHANGES As supplied, the HSIO-4 is ready for immediate connection to four asynchronous RS-232 terminals or printers. If you are using the North Star TSS/A Multi-User System for Application Software with asynchronous RS-232 terminals and printers, the HSIO-4 can be installed directly in the HORIZON without modification.

  • Page 12: Completing Installation

    Remove the four screws that hold the HORIZON cover in place. Lift off the cover. Hold the HSIO-4 board in one hand and touch the metal chassis of the HORIZON with the other hand. This will eliminate any difference in static potential between the HSIO-4 board and the computer.
  • Page 13 The top of the HSIO-4 board should be even with the other installed North Star boards. If a second HSIO-4 board is utilized, it should be installed in the slot immediately in front of the first HSIO-4 board.
  • Page 14 Four flat ribbon cables are supplied with the HSIO-4 board. You will notice that each cable has a connector at either end. The Terminal/ Modem Mating Connector is shaped like an elongated "D" and has curved corners. The Board Mating Connector is rectangular.
  • Page 15 Gently pull the cable through until the Terminal/Modem Mating Connector touches the sides of the hole. From outside the back panel, push firmly to seat the connector in the hole. Board Mating Connector Terminal/Modem Mating Connector North Star HSIO-4 User/Technical Manual...
  • Page 16 D-connector in place, as shown in Figure 2-10. From outside the back panel, insert each screw through the connector mounting. Slip a lockwasher over the screw, and secure it with a nut. Repeat these installation procedures for all four ribbon cables. North Star HSIO-4 User/Technical Manual...
  • Page 17 Taking care not to twist the cables, plug each Board Mating Connector into the appropriate 26-pin header at the top of the HSIO-4 board. See Figure 2-11. For use with the TSS/A, the cables should be connected as follows: J1 to Port 2...
  • Page 18 I/O port sockets on the HORIZON back panel. Plug the HORIZON line cord into the wall outlet. Plug the power cords for all connected terminals into the wall outlet. Turn on the power switches for the HORIZON and all terminals. North Star HSIO-4 User/Technical Manual...

  • Page 19: Implementing Hsio-4 Features

    This section provides an overview of serial data communication between computers and other electronic devices; it also provides detailed instructions on how to use the HSIO-4 to establish communication links between the computer and a variety of periperal devices. As supplied, the HSIO-4 is ready for immediate connection to four asynchronous RS-232 terminals or printers.

  • Page 20: Establishing A Communication Link

    RS-232 signals. A few commercially used terminals, such as teletypes, use 20mA current loop signals. As supplied, each HSIO-4 port is wired to use RS-232 signals. 20mA current loop signals can be accomodated with a configuration change. Refer to section 3.2.5 for specific instructions.
  • Page 21 COMPUTER TO TERMINAL COMMUNICATION If the HORIZON is to communicate with a serial terminal (such as a video terminal or a printer) , the interfacing port on the HSIO-4 must be configured to simulate a modem. COMPUTER TO MODEM COMMUNICATION...
  • Page 22 HORIZON and another computer that simulates a modem, you must configure an HSIO-4 port to simulate a terminal. To configure an HSIO-4 port as a terminal, you must wire the Configuration Header for the relevant port according to the specific procedures in Section 3.2.2 for asynchronous...
  • Page 23 Section 3.2.4 (asynchronous) and Section J.3.5 (synchronous). In addition, the complete manufacturer specification lot the USART is reproduced in Appendix B, alomj with notes on the interface to the USART. North Star HSIO-4 User/Technical Manual...
  • Page 24 3.1.2 HS10-4 BOARD LAYOUT Before proceeding to implement any of the features treated in this section, please note: The four ports on the HSIO-4 board are identically arranged; they are labeled alphabetically from left to right as shown below. CONFIGURATION...

  • Page 25: I/O Addresses

    3.1.3 I/O ADDRESSES The HSIO-4 requires 16 consecutive I/O addresses. (All addresses referenced in this section are I/O addresses.) Each of the four ports uses four consecutive addresses. Addresses start at XOH and run to XFH. (X represents a hexadecimal digit which is set by switches on the board.)
  • Page 26 I/O ADDRESS SWITCH SETTINGS Starting Switch Number Reserved Address Regions Address ____M ____A5____ A4 Used by the HORIZON motherboard Reserved for North Star use 7 OH Reserved for North Star use Used by North Star RAM boards North Star HSIO-4 User/Technical Manual...

  • Page 27: Interrupts

    Each HSIO-4 port provides four interrupt sources. Three may be armed and disarmed under program control; the fourth. Synchronous Detect, is armed by a jumper on the HSIO-4 board. Consult Section 3.4 for instructions on how to program the interrupts and connect interrupt sources to the S-100 bus interrupt lines.

  • Page 29: Asynchronous Operation

    HORIZON is to communicate with a serial terminal (such as a video terminal, a teletype, or a printer), then the relevant HSIO-4 port must be configured to simulate a modem. Similarly, if the HORIZON is to communicate with a modem, then the relevant HSIO-4 port must simulate a terminal.

  • Page 30: Configuring Port As Terminal

    If the HORIZON is to communicate with a modem (or with another computer simulating a modem), the interfacing HSIO-4 port must be configured to simulate a terminal. Configure an HSIO-4 port as a terminal as follows: Carefully remove the shunt from the Configuration Header socket and replace it...

  • Page 31: Baud Rate Selection

    3.2.3 BAUD RATE SELECTION The baud rate for each HSIO-4 port is programmable and can be selected from among a total of ten available asynchronous baud rates. See Table 3-3 below. Table 3-3 ASYNCHRONOUS BAUD RATES Alternatives Output Standard Value...
  • Page 32 To determine the Baud Rate Select Address, consult Tables 3-1 and 3-2 (in Section 3.1.3). FOR EXAMPLE: Assuming the HSIO-4 board is addressed starting at 10H, you would set the baud rate to 300 on port B by outputting 06H...
  • Page 33 55.8KHZ • • • specify and the nearest pin marked "04H." Figure 3-10, for example, shows where to Figure 3-10 install the mini-jump to specify 75 baud. North Star HSIO-4 User/Technical Manual...

  • Page 34: Sample Program

    3.2.4 SAMPLE PROGRAM This section provides an example of how to program the four HSIO-4 ports for use with four asynchronous RS-232 terminals and/or printers. Programming other configurations requires a detailed familiarity with USART operation. For the convenience of the programmer, a complete manufacturer data sheet for the USART is reproduced in Appendix B.
  • Page 35 0000 ; Sample asynchronous I/O routines for HSIO-4 0000 0000 • 0010 BASE ;Address of HSIO-4 0010 PORTA BASE+00H ;Address of port A 0014 PORTB BASE+04H ;Address of port B 0018 PORTC BASE+08H ;Address of port C 001C PORTD BASE+0CH ;Address of port D...
  • Page 36 ;Mask off top bit 0047 E67F 0049 004A PORTD+USTA ;Check USART status 004A DB1F COUTD ;Get TxReady bit 004C E601 004E 28FA COUTD ;Wait tili ready ;Output char is in B 0050 D31F PORTD+USTA ;Output character 0051 0053 North Star HSIO-4 User/Technical Manual...
  • Page 37 PORTB+UDAT 0080 DB16 PORTC+UDAT 0082 DB1A 0084 DB1E PORTD+UDAT 0086 0087 • USTAT PORTA+USTA ;Output command to 0087 D313 0089 D317 PORTB+USTA ;A11 HSIO-4 channels 008B D31B PORTC+USTA 008D D31F PORTD+USTA 008F 0090 • 0090 North Star HSIO-4 User/Technical Manual...

  • Page 38: Current Loop Operation

    A teletype is a passive device; it does not supply current, but relies on current supplied by the HSIO-4. The HSIO-4 is not equipped to communicate with active current loop devices such as computers that produce current loop signals.
  • Page 39 Connect a 25-pin D-type connector to the terminal cable as follows: pin 9 to the printer "+" lead pin 3 to the printer lead pin 2 to the keyboard "+" lead pin 10 to the keyboard lead North Star HSIO-4 User/Technical Manual...

  • Page 40: Buffer Full Signals

    As supplied, the HSIO-4 expects the buffer full signal on pin 20. Some printers, however, use pin 19. Printers using pin 19 require the...
  • Page 41 #2 (See Figure 3-12). Figure 3-12 On the component side of the board, install a mini-jump between the center pin and pin #1. (The pin numbers are printed on the component side of the board.) North Star HSIO-4 User/Technical Manual...
  • Page 42 North Star HSIO-4 User/Technical Manual...
  • Page 43 As supplied, all four HSIO-4 ports are configured for asynchronous operation. Each port can be reconfigured for synchronous operation (see Sections 3.3.1. and 3.3.2).
  • Page 44 16 15 14 13 12 11 10 Configuration Header. TTFTTffl 4 5 6 Figure 3-13 Take an 8-pin shunt and install it, with all four links connected (as shown in Figure 3-14), in the Clock Header socket. Figure 3-14 North Star HSIO-4 User/Technical Manual...
  • Page 45 Wire an 8-pin header as follows, and install it in the Clock Header socket. pin 1 to pin 2 pin 3 to pin 6 pin 4 to pin 5 pin 7 to pin 8 Figure 3-16 North Star HSIO-4 User/Technical Manual...
  • Page 46 Take an 8-pin shunt, disconnect the link between pin 3 and pin 6, and install it in the Clock Header socket. Figure 3-18 Refer to Section 3.3.3 for instructions on programming baud rates for synchronous operation. North Star HSIO-4 User/Technical Manual...
  • Page 47 Clock Header socket. pin 1 to pin 2 pin 4 to pin 5 pin 7 to pin 8 Figure 3-20 Refer to Section 3.3.3 for instructions on programming baud rates for synchronous operation. North Star HSIO-4 User/Technical Manual...
  • Page 48 3.3.3 PROGRAMMING BAUD RATES When configured for synchronous operation with programmable baud rates, an HSIO-4 port can transmit data at any one of five programmable baud rates. See Table 3-6 below. An additional jumper change enables three additional programmable baud rates. (For specific instructions, see Section 3.3.4.)
  • Page 49 Address for the relevant port. To determine the Baud Rate Select Address, consult Table 3-1 (in Section 3.1.3). For example, assuming the HSIO-4 board is addressed starting at 10H, you would set the baud rate to 4800 on port B by outputting...
  • Page 50 "Alternatives (With Jumper Change)" can be made available as described below. Please Note: Such a jumper change effects all four HSIO-4 ports. Locate JP13, turn the board so that the solder side faces up, and cut one of the traces as directed below.
  • Page 51 3.3.5 SAMPLE PROGRAM This section provides a very basic example of how to program a USART in the HSIO-4 for synchronous operation. Programming for specific applications requires a detailed familiarity with USART operation. It is beyond the scope of this manual to provide specific instructions on programing for such applications.
  • Page 52 HSIO-4 for synchronous operation ; Sample routines to 0000 0000 • 0000 • ; Start of text character 0002 ; End of text character 0003 ; Data Link Escape character 0010 ; Sync character 0016 0000 • ; USART status bits...
  • Page 53 00 4E 18E5 SDATA Get next byte 004F • 0051 • 0051 GETCH Get char from serial port DB13 CTRL • 0053 E602 RXRDY 0055 28FA GETCH Wait till done • 0057 DB12 DATA 0059 North Star HSIO-4 User/Technical Manual...
  • Page 54 Get USART status DB13 CTRL 0092 Check if ready for character AN I TXRDY 0094 E601 Wait till it is 0096 28FA Get character back and 0098 0099 D312 DATA output 009B 009C • 009C User/Technical Manual North Star HSIO-4...
  • Page 55 The first three interrupt sources are armed and disarmed under program control; the fourth interrupt source, Synchronous Detect, is armed by a mini-jump on the HSIO-4 board. The resultant interrupt from each port can be connected to any of the S-100 interrupt lines.
  • Page 56 Table 3-1 shows the Interrupt Mask Set addresses for each port. For example: Assuming that the HSIO-4 board is addressed starting at 10H, to arm the Tx Ready interrupt (and disarm the other two...
  • Page 57 Bit 0 is the least significant bit. All interrupt mask bits are disarmed when the computer is powered up or reset. Table 3-9 1 = Arm 0 = Disarm EIGHT POSSIBLE BIT PATTERNS Rx Ready Value SX R.ea.dy Tx,.Empty. 07 H North Star HSIO-4 User/Technical Manual...
  • Page 58 3.4.2 ARMING THE SYNCHRONOUS DETECT INTERRUPT As supplied, the Synchronous Detect interrupt for each HSIO-4 port is disarmed. The Synchronous Detect interrupt can be armed by a mini-jump. To arm a Synchronous Detect interrupt: Locate the 3-pin jumper area to the right...
  • Page 59 3.4.3 CONNECTING THE INTERRUPT LINES The HSIO-4 board provides access to ten S-100 bus interrupt lines. These can cause eight vectored interrupts (VIO - VI7), a non-vectored interrupt (PINT), and a non-maskable interrupt (NMI). Each port provides four sources of interrupt.
  • Page 60 (VI2), you would wire pin 1 to pin 12 on a 14- pin header, as shown below: Figure 3-26 As supplied, the interrupts for each HSIO-4 port are all wired to S-100 bus interrupt line VI2, as shown in Figure 3-27. <...
  • Page 61 SECTION 4 THEORY OF OPERATION The HSIO-4 board consists of four independent serial I/O ports, and some common control logic. The major common functional blocks are the I/O Address Decoder, the Data Buffers, the Baud Rate Generator, and the Interrupt Header.
  • Page 62 I/O ports. The HSIO-4 board is selected by address bits A4 - A7. These address bits are compared with the address switches. If a match occurs, the board is selected.
  • Page 63 Out (DO) and Data In (DI) lines to a single bidirectional bus on the HSIO-4. During S-100 bus writes, the Data Buffers gate data from the S-100 DO bus onto the HSIO-4 internal bus. During USART reads, the buffers gate the read data onto the S-100 DI bus.
  • Page 64 S-100 bus interrupt lines. More than one I/O port interrupt signal may be connected to one S-100 bus interrupt line. As supplied, all four port interrupt signals are connected to the S-100 bus interrupt VI2. North Star HSIO-4 User/Technical Manual...
  • Page 65 BUFFER BUFFER AND TIMING BAUD INTERRUPT RATE SELECT SELECT I /O PORT Ü I / O DATA BUFFERS INTERRUPT BAUD RATE HEADER AODRESS GENERATOR DECODER FUNCTIONAL BLOCK DIAGRAM OF AN INDIVIDUAL I/O PORT Figure 4-2 North Star HSIO-4 User/Technical Manual...
  • Page 66 Various connections on the Configuration Header and the Clock Header for a port permit several types of serial transmission. The header configurations determine how the USART connects to the port connector and the baud rate signals. North Star HSIO-4 User/Technical Manual...
  • Page 67 Configuration Header. To use the 55800 Hz signal, the Configuraton and Clock Headers can be wired to use the 55800 Hz signal ONLY and not the selectable rates. North Star HSIO-4 User/Technical Manual...
  • Page 68 Bit 0 arms the TRANSMIT EMPTY SIGNAL Bit 1 arms the TRANSMIT READY SIGNAL Bit 2 arms the RECEIVE READY SIGNAL The Synchronous Detect Flag, which is armed by a mini-jump, is only used for synchronous transmission. North Star HSIO-4 User/Technical Manual...
  • Page 69 HSIO-4 board, you must first determine whether the cause of the failure is in a specific peripheral device and its cabling to the computer or in the HSIO-4 board itself. Use the following procedure to trace the cause...
  • Page 70 This procedure utilizes a feature, supported by DOS and BASIC, known as "auto-start," which automatically loads BASIC and runs the HSIO-4 test. Once a test diskette has been set up, restarting the computer with the reset switch prompts DOS to load BASIC, which, in turn, starts the HSIO-4 test.
  • Page 71 REMark statements (which have been added only to explain the test process). List the program to verify that it has been correctly entered into BASIC. Save this test program on the diskette by typing: NSAVE HSIOTEST North Star HSIO-4 User/Technical Manual...
  • Page 72 11 REM PROGRAM NAME= HSIOTEST 8-April-81 12 !TAB(10),"North Star HSIO-4 Test" \! REM Set up port addresses for first HSIO-4 port— REM Edit B for non-standard address' 15 B=16 \REM Base address of HSIO-4 =10 hex. 16 D=B+2 \REM USART data port address.
  • Page 73 20 WRITE #1 % 15 , & 0 , NOENDMARK 30 CLOSE #1 Restart the computer with the reset switch. The HSIO-4 test sign-on prompt ("North Star HSIO-4 Test") should appear on the screen. If this sign-on prompt does not display, check to make sure that the procedures in Section 5.1.
  • Page 74 Insert the test diskette in drive one and restart the computer with the reset switch. The HSIO-4 sign-on message ("North Star HSIO-4 Test") should appear on the screen, followed by this prompt: Test port [A, B, C, D]: Before selecting the port to be tested, you must connect pin 2 and pin 3 at the connector for the port to be tested.
  • Page 75 (1489)— to pin 3 (RXD) of the USART. Check to make sure that the test fixture is installed properly. Port IA,B,C,D] transmitted [value] received as [value] If the value received differs from the value transmitted, the suspected components are 6F, 7F or the USART. North Star HSIO-4 User/Technical Manual...
  • Page 76 OSCILLOSCOPE TESTING If all four I/O ports fail to communicate with peripheral devices or fail to pass the HSIO-4 test, this indicates that the problem is probably in the power circuitry or the Baud Rate Generator circuitry. The following procedure for checking this circuitry requires the use of an oscilloscope with a bandwidth of at least 10 Megahertz.
  • Page 77 3E pin 1 13us 26us 53us 1200 baud 3E pin 15 27us 52us 105us 3E pin 14 53us 600 baud 105us 210us 300 baud 3E pin 13 105us 365us 575us 110 baud 3E pin 12 210us North Star HSIO-4 User/Technical Manual...
  • Page 78 REPAIR PROCEDURES If you identify malfunctions or defective components that you are unable to rectify or replace yourself, you can return a defective HSIO-4 board to any North Star Authorized Service Center for repair. North Star HSIO-4 User/Technical Manual...
  • Page 79 No Connection No Connection No Connection Receive Clock M to T No Connection Secondary RTS Optional Use Data Terminal Ready T to M No Connection No Connection No Connection Transmit Clock T to M No Connection North Star HSIO-4 User/Technical Manual...
  • Page 80 HSIO-4. Specifically, the SYNDET pin can be used only as an output with the HSIO-4. It cannot be used as an input to initiate HUNT mode. When HUNT mode is required, it must be set by the appropriate command instruction.
  • Page 81 Transmitter Ready (ready for char from 8080) Data Set Ready Data Terminal Ready SYNDET Sync Detect Request to Send Data Clear to Send Data Transmitter Empty ♦5 Volt Supply v Cc SYNDET G N D Ground TxRDY North Star HSIO-4 User/Technical Manual...
  • Page 82 Exposure to absolute maximum rating conditions for extended periods may äffect device reliability. * T a = 25° C North Star HSIO-4 User/Technical Manual...
  • Page 83 0.098 2.54 0.10 0.02 + 0.004 0.5 ± 0.1 33.02 0.059 2.54 M IN. 0.10 MIN. 0.02 MIN. 0.5 MIN. 5.22 MAX. 0.205 MAX. 0.225 MAX. 5.72 MAX. 15.24 0.52 13.2 „ + 0.004 0.002 North Star HSIO-4 User/Technical Manual...
  • Page 84 For 16X and 64X Baud Rate, »Tx o r lqx < 1/(4,5 t^yl -100 -5 0 +100 A CAPACITANCE (pF) Figure 1. Typical A Output Delay Versus A Capacitance (pF) TEST LOAD CIRCUIT North Star HSIO-4 User/Technical Manual...
  • Page 85 TIMING WAVEFORMS " • --------------------------' C Y — — — — " “ C L K ___________ ____________________ a c ---------------------------------- \ C O cs ~ — p----- ------------- — ■ ' 0 7 Do — ----- IQW ---- — IRA—...
  • Page 86 Modem Request to Send line. A "zero" on the Clear to Send input enables the Clear to Send USART to transmit serial data if the TxEN bit in the Command Instruction register is enabled (one). North Star HSIO-4 User/Technical Manual...
  • Page 87 1 AIM U A n U O T ö 1 tIV I B U S CONTROL BUS I/O R I/O w RESET (TTL) DATA BUS c ______ _______; '______ £ ■ D ; - Do RESET 8251 North Star HSIO-4 User/Technical Manual...
  • Page 88 RxC or TxC equals 300 Hz (lx ) A or S RxC or TxC equals 1.76 KHz (16x) RxC or TxC equals 4800 Hz (16x) A only RxC or TxC equals 7.04 KHz (64x) RxC or TxC equals 19.2 KHz (64x) A only North Star HSIO-4 User/Technical Manual...
  • Page 89 Command Instruction updates may occur at any time during the data block. To modify the Mode Instruction, a b it may be set in the Command Instruction which causes an internal Reset which allows a new Mode Instruction to be accepted. North Star HSIO-4 User/Technical Manual...
  • Page 90 (OE) is set. All the error flags can be reset by setting a b it in the Command Instruction. Error flag conditions w ill not stop subsequent USART operation. North Star HSIO-4 User/Techpical Manual...
  • Page 91 DATA CHARACTER ---------------------------- ( $ ------------------------ N O T E © IF CHARACTER LENGTH IS DEFINED AS 5. 6. OR 7 BITS; THE UNUSED BITS ARE SET TO "Z E R O ." RECEIVE FORMAT North Star HSIO-4 User/Technical Manual...
  • Page 92 SYNCHRONOUS As in Asynchronous transmission, the TxD output remains "h igh " (marking) TRANSMISSION until the juPD8251 receives the first character from the processor which is usually a SYNC character. After a Command Instruction has set TxEN and after Clear to Send (CTS) goes low, the first character is serially transmitted.
  • Page 93 CHAR 2 ---------------------------- ------------------------- TRANSMIT FORMAT SERIAL DATA INPUT (RxD) ------------ * * ----------- SYNC SYNC DATA CHARACTERS CHAR 1 CHAR 2 ---------------------------- ------------------------- CPU BYTES <5-8 BITS/CHAR) ------- ------- DATA CHARACTERS ------- ------ RECEIVE FORMAT North Star HSIO-4 User/Technical Manual...
  • Page 94 If a valid STOP bit is not detected at the end o f a character, the FE flag is set, and is cleared by setting the ER bit in a subsequent Command Instruction. FE being set does not inhibit USART operation. Note: (D ASYNC mode only. North Star HSIO-4 User/Technical Manual...
  • Page 95 T x R D Y s t a t u s b i t ■ D B B u f f e r E m p t y T x R D Y ( p m 1 5 ) - D B B u f f e r E m p t y • C T S • T x E n North Star HSIO-4 User/Technical Manual...
  • Page 96 APPLICATION OF THE PD8251 ASYNCHRONOUS SERIAL INTERFACE TO CRT TERMINAL, DC to 9600 BAUD AOORESS BUS CONTROL BUS DATA BUS R»D T«0 PHONE LINE ASYNC INTER MO D E M FACE BAUD r T c RATE GENERATOR TELEPHONE LINE ASYNCHRONOUS INTERFACE TO TELEPHONE LINES SYNCHRONOUS INTERFACE TO TERMINAL OR PERIPHERAL DEVICE ADDRESS BUS CONTROL BUS...
  • Page 97 APPENDIX C HSIO-4 PARTS LIST PL 00135A PZü DESCRIPTION HSIO-4 PC BOARD 00133 3D,4D,6D,8D 43003 IC 74LS03 43008 IC 74LS13 IC 74LS14 43009 43012 IC 74LS32 43020 IC 74LS136 43022 IC 74LS139 3E,3F,4E,4F 43024 IC 74LS151 43027 IC 74LS161 2D, 1F...
  • Page 98 HEX NUT, 6-32 SCREW, 6-32 x 5/16 38017 38042 HEATSINK, 6106B-14 EJECTOR, CIRCUIT CARD 38080 38064 JACKSCREW KITS, D-CONNECTOR (Each kit contains: 2 jackscrews, 2 nuts, and 2 bolts) RIBBON CABLE, HSIO-4 00144 00187B HSIO-4 USER/TECHNICAL MANUAL North Star HSIO-4 User/Technical Manual...
  • Page 99 N o r t h S l a r ^ North Star Com puters, Inc. 14440 Catalina St., San Leandro, CA 94577 USA (415) 357-8500 TWX/Telex (910) 366-7001...
  • Page 100 N o r t h S l a r ^ North Star Com puters, Inc. 14440 Catalina St., San Leandro, CA 94577 USA (415) 357-8500 TWX/Telex (910) 366-7001...

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