Instruction Manual
Model 411S
SCSI Bus CAMAC Highway Driver

Second Edition  2.1

The Jorway Corporation
27 Bond Street
Westbury, NY 11590
(516)-997-8120

1.0  Introduction

 This manual describes the installation, operation, and programming of the Jorway Model 411S SCSI CAMAC highway driver.  It is assumed that the user is familiar with the CAMAC system, as described in IEEE Standards 583 and 675.  Knowledge of the SCSI-2 specification, ANSI Standard X3.131, while not required, will be helpful, especially in writing software using the SCSI message system and interpreting the controller's replies to various SCSI commands.

     NOTE:

  To avoid confusion with the software entity of the same name, the
  Model 411S will be referred to in this document as a "controller"
  at the risk of confusion with the crate controllers to which it
  is connected.

 2.0  General Description

 The Jorway Model 411S is a 3 1/2 inch rack mounted instrument that interfaces a multi-crate CAMAC data acquisition system to any computer supporting the ANSI standard Small Computer System Interface (SCSI) Bus.  The CAMAC system can consist of up to seven CAMAC crates on the parallel Branch Highway and up to 63 Crates on the Serial Highway.  Models with the Enhanced  Serial Driver provide data transfers  in special block modes capable of operating at 3 megabytes per second.

 The Model 411S is also available as a conversion kit for existing  Unibus or Q-bus models in  a 5 1/4 inch chassis.  Connection to the SCSI bus, and the Serial  and Parallel Highway ports is at the rear of the chassis.  New Model 411S models are housed in a 3 1/2 inch rack mounted chassis with the SCSI and Highway ports at the front panel.  Various configurations are available supporting  the CAMAC parallel Branch Highway or the Serial Highway or both.

  Model 411-2429  Parallel Branch  Highway
  Model 411-2472  Serial Highway
  Model 411-2572  Enhanced Serial Highway
  Model 411-2472  Parallel Branch Highway and Serial Highway
  Model 411-2572  Parallel Branch Highway and Enhanced Serial Highway

Option 1 is available on the Model 411S(which provides a single powered CAMAC module slot). This slot is commonly used to house a Serial U port or Bypass CAMAC module. This allows the Model 411S with Serial Driver to use the identical module that is used in the CAMAC crate. The Option 1 chassis is 5 1/4 inch  high(of greater depth than the 3 1/2 chassis) to accommodate the module slot. Other options are also available such as operation on 115 or 230 VAC, 50 or 60 Hz.

 A Model 411S can be intermixed with other SCSI devices on a single SCSI port, which can support up to 7 devices. The standard model uses the single-ended  protocol, which allows a SCSI bus length of six meters; as an option the differential SCSI bus can be employed to allow a length of 25 meters. The Model 411S has two SCSI-2 low density connectors at the front, allowing SCSI devices to be daisy-chained.  If not daisy-chained, one connector is used for a SCSI terminator.

 The Model 411S obeys all mandatory requirements in the SCSI-2 specification.  All types of CAMAC operations are permitted, including high-speed Block Transfers under hardware control. Any of seven block transfer modes can be selected, including THE ESONE standard modes Address Scan, Q-Stop, Q-Repeat, Stop-on Word as well as Fermilab extended subaddress scan.  During block transfers, only data is transferred on the SCSI Bus.  For any transfer, the user can elect to transfer either two or three data bytes for each CAMAC cycle.  In the latter case, an additional null byte is inserted in the data stream so that 24 bit data is aligned on 32 bit memory boundaries.  The order of byte transmission is user selectable as high-order first or low-order first.
 
 16K bytes of data is FIFO buffered within the Model 411S.  In addition, the 411S can utilize the SCSI disconnection/reselection protocol and can transfer data at a rate of 5 Mbytes/sec on the SCSI bus in synchronous SCSI mode. It can, therefore, acquire a block of data at CAMAC speed up to 3 Mbytes/sec while disconnected from the SCSI bus, and then connect to the SCSI bus and transfer the data at the higher rate. This allows efficient use of the SCSI bus bandwidth, which may be shared with other devices such as disks. CAMAC transfers are not interrupted by the disconnection/reselection process, but proceed continuously until the transfer length is satisfied. The burst size, i.e., the number of bytes transferred on the SCSI bus after a reselection, is user selectable at 1/8, 1/4, or 1/2 of the FIFO buffer size.

 Modules asserting LAM's can interrupt the computer using the SCSI Asynchronous Event Notification (AEN) protocol. In the course of this protocol, the Model 411S becomes a (temporary) SCSI Initiator, selects the host adapter as a Target, and sends the pattern of asserted LAM's to the host. If this protocol is enabled, and a LAM occurs on the parallel Branch Highway, a GL operation is automatically performed, and the result transferred in 4 bytes. If the LAM is from the Serial Highway, the contents of the serial demand stack is transmitted. For this protocol to be successful, the host adapter must be capable of acting as a SCSI target. Alternatively, the user can perform a GL operation or read the serial demand stack by performing a CAMAC read addressed to parallel or serial crate 0.

 The top PC board in the S411 has a single 8-position DIP switch and 3 straps that must be positioned (on posts) before operation. Switches 1(LSB) - 3(MSB) establish the binary encoded SCSI ID of the 411S. An "ON" switch represents a binary 0. Switches 4 - 6 are presently  unused, and should be OFF. If disconnection is enabled , switches 7 & 8 determine the number of bytes transferred after each selection as follows:
 

 The SCSI bus must be terminated at both ends by resistor networks or their equivalents, which requires power. A wire in the SCSI cable is dedicated to this purpose. The SCSI Standard states that
this line must be powered by all SCSI "Initiators". The Host interface normally serves this function as well as providing back termination of the Bus. Therefore, a SCSI terminator plug must be inserted in the unused bus connector of the last device on the Bus. The model 411S is capable of powering the SCSI terminator, but this feature is normally disabled by removing 1 ampere fuse F1.

3.0 Programming

 In order to issue a command to the Model 411S, the host interface must perform the following tasks in the appropriate SCSI Bus phase. Many of these tasks are automatically performed, in a fashion transparent to the user, by the port driver provided by many processor vendors.

  1. Bus Arbitration
  2. Select the Controller
  3. Send the Identify message
  4. Send the Command Descriptor Block
  5. Send or Receive Data
  6. Receive the Status Byte
  7. Receive the Command Complete Message

 Bus Arbitration is only required if there are devices on the bus, other than the host interface, that might become SCSI Initiators. Note that the Model 411S Controller can become a (temporary) Initiator
for the purpose of transmitting a LAM message. Therefore, arbitration by the host is required if LAM's are enabled. The hardware of the host SCSI interface normally performs the Arbitration procedure, but this can be skipped if there are no other potential Initiators.

 The Controller is selected by asserting the SCSI Data line corresponding to the Controller ID together with the SCSI SEL signal. The line associated with the host ID may optionally be included. The selected Controller will respond by asserting the SCSI BSY signal and enter target mode. The SCSI target determines the type and direction of data transfer on the bus by controlling the signals C/D, I/O, and MSG. These signals determine the bus "Phase" in accordance with the following table:
 

 In accordance with the SCSI-2 specification, the host should select the model 411S with the ATN signal asserted, causing the controller to enter the Message Out phase initially. The Controller then expects the host to send a one byte IDENTIFY message that selects the logical unit within the target. This message is described in section 7.
 

  1.  INQUIRY
  2.  TEST UNIT READY
  3.  REQUEST SENSE
  4.  CAMAC Commands

 The Command Descriptor Blocks accepted by the Model 411S are either 6 or 10 bytes long and will be described in the next section. Following the Command Phase, the Controller will enter Data Phase if the command involves a data transfer, is valid, and contains no errors. Following this, the Controller will enter Status Phase and send one byte of status. If the command is invalid, does not involve a data transfer, or for some reason cannot be performed, the Controller will proceed directly from Command Phase to Status Phase. Only three possible status bytes are generated by the Model 411S:
 

3.1 INQUIRY Command

 The INQUIRY command may be issued at any time to determine the characteristics of any logical unit on any target. Thirty-six bytes of information are returned indicating the type of device attached, the manufacturer, model number, and revision level. This command is generally issued by an operating system at start-up but may be issued by a user. The Command Descriptor Block is as follows:

 The data returned by the Model 411S conforms to Table 7-15 of the SCSI Standard. The Peripheral Device Type will be 1 Fh. The Peripheral Qualifier will be 000b. If a non-zero logical unit is specified in the preceding IDENTIFY message, the Peripheral Qualifier will be 011b. The INQUIRY command will return GOOD Status unless an improper bit is detected in the Command Descriptor Block.
 
 

3.2 TEST UNIT READY Command

 The TEST UNIT READY command is a rapid way to determine, if the Controller is ready to accept data transfer commands, since there is no associated data phase. The TEST UNIT READY command returns GOOD status if the Controller is ready. There is one situation in which it may not be ready and will return CHECK CONDITION status in response to this command: the UNIT ATTENTION condition. The UNIT ATTENTION condition is established at power-up by SCSI Bus Reset or by receipt of a BUS DEVICE RESET message. While the UNIT ATTENTION condition exists, CAMAC commands and the TEST UNIT READY command return CHECK CONDITION status, and CAMAC commands cannot execute. After this status is transmitted, a "Contingent Allegiance" is said to exist, and the UNIT ATTENTION is cleared. A REQUEST SENSE command, if issued at this time, would return a Sense Key indicating UNIT ATTENTION. Note that the sense data is cleared after a REQUEST SENSE command, or if another TEST UNIT READY or CAMAC command is issued.
 

The format of the TEST UNIT READY command follows:

The Logical Unit field, Reserved fields, and all fields of byte 5 should be 0.  If any are non-zero, CHECK CONDITION status will be returned and a Sense Key of "illegal request" established for a future REQUEST SENSE command. A similar result will be obtained if the preceding  IDENTIFY message specified a non-zero logical unit. The two conditions differ in the "Additional Sense Code", as noted later.

3.3 REQUEST SENSE Command
 The REQUEST SENSE command is normally issued, after a CHECK CONDITION status is returned by any command, to determine the reason. The format of the Command Descriptor Block follows:

 The following Sense Keys may be returned by the Model 411S: 

In those cases where the sense key leaves some doubt as to the exact cause of an error, the Additional Sense Code provides more specifics. The following ASC's from the SCSI-2 Standard may be encountered: 

3.4 CAMAC Commands

 The SCSI Standard does not provide for a device like a CAMAC highway controller. Therefore, non-standard Command Descriptor Blocks are used following the IDENTIFY message of the SCSI-2 specification. Both 6 and 10 byte commands are used; the former for non-data transfers, and the
latter for data transfers.

3.4.1 CAMAC Non-Data Commands

 A CAMAC non-data command has a function code between 8 and 15, or between 24 and 31 (the F8 bit set).  The Command Descriptor Block for a non-data CAMAC command consists of 6 bytes, as follows:

                         NOTE:
  Unlike Unibus and Q-Bus versions of the Model 411, 7 crates can exist
  on the parallel highway even if a serial highway is simultaneously
  active. The PAR ONLY switch found on these units is inactive or omitted
  in the SCSI units.

 After the command is executed, the Controller proceeds to the Status Phase and returns one of the following status bytes, then the Command Complete message (which is null):

If CHECK CONDITION status is returned, the REQUEST SENSE command may be issued to determine the reason.

3.4.2 CAMAC Data Transfers

 CAMAC data transfers use the same Operation Code (Byte 0) for reads and writes, unlike other SCSI commands. The distinction is conveyed in the CAMAC Function Code within the Command Descriptor Block. Data transfers may made in either 16 or 24 bit mode. The former only transfers data on the low order 16 data lines of the CAMAC Dataway; therefore, it requires only two bytes to transfer a CAMAC word on the SCSI Bus. In 24 bit mode, all Dataway data lines are used, and three bytes are required for each Dataway cycle. In order to align memory data on full word boundaries in 24 bit mode, a null byte is inserted in the SCSI data stream as the most significant byte of each CAMAC word transferred. Transfer lengths are always stated in bytes; therefore, it will be two or four times the number of CAMAC words involved.
 

                            NOTE:

  When using 16-bit mode Inexperienced CAMAC users are often
  disturbed to find non-zero bits appearing on the high order eight
  Dataway write lines (W17-W24). This is unavoidable, as the Dataway
  is "hard-wired" to use 24 bits. If it is desired to use 16-bit mode with
  modules sensitive to all 24 bits, a single 24 bit write command may be
  issued with a null high order byte. Following this, 16 bit mode may be
  used, and the high order bits will be 0.

 CAMAC data transfers use a 10 byte Command Descriptor Block as follows:

 The S/P bit selects between the serial or parallel CAMAC highway, as noted above. Bytes 6 through 8 specify the transfer length IN BYTES, which may be as long as 16 Mbytes. The DD bit disables SCSI disconnection and reselection on a command by command basis, if it has been enabled by operating system level software.

3.4.3 Block Transfer Modes

 The M3 M2 and M1 bits specify the mode of transfer.   Models with Enhanced Serial Drivers (411S-2572 and 411S-2573) have two additional modes for enhanced serial transfers as well as an additional Q-Ignore transfer mode.  Enhanced serial transfers  require a type L-2 crate controller supporting Enhanced operations such as the Jorway Model 174 (L-2 controller with Block Modes).

 The M3 M2 and M1 bits specify the mode of transfer as follows:

 In Q-Stop, Q-Repeat, or  Stop-on-Word mode, the Station, and Subaddress remain fixed at the initial value. In Q-Stop and Stop-on-Word, the transfer terminates if Q = 0. In the former mode, data from the cycle giving Q = 0 is not transferred; in the latter, it is. Stop-on-Word is useful for single word (2 or 4 byte) reads of  module status registers which often do not return Q), or block reads of memories that drop Q on the last valid word.

 In repeat mode, data is not transferred if Q = 0, but CAMAC cycles continue. All transfer modes terminate if the transfer length is satisfied or an error occurs, and the Controller proceeds to the Status Phase. Note that it is not possible to transfer an odd number of bytes of CAMAC data, although an odd transfer length is permissible for the INQUIRY or REQUEST SENSE commands.

 In Enhanced serial block operation two modes are available, Q-Stop and Q-Ignore.     Enhanced  Q-Stop serial block mode  operates with read or write commands and will terminate the block transfer on either  (1) a Q = 0 response from the module  during  the serial block operation , (2) transfer length satisfied or  (3) error. Because there will be serial operations  in the serial highway pipeline when  any of these conditions occur  additional operations may be performed at the module which cannot be accounted for (Overrun).  Enhanced Q-Ignore serial block mode operations count the transfers being requested on the serial highway instead of transfers completed as is done in Q-Stop. When the requested wordcount is satisfied, the transmitted commands for dataway  operations  at the crate controller terminate.  As a result there is no Overrun at the module. The receiver portion of the serial driver waits for the operations in the serial pipeline to complete and if no errors are detected (i.e. parity checksum OK), the block transfer  is completed successfully. If errors occur during the block transfer , operations at the module may be indeterminate.  Operations in Enhanced serial block mode Q-Ignore return status of  Q = 0 for all operations.

4.4.4  CAMAC Errors

 CAMAC data transfer commands return only three possible status bytes, as noted above. If the transfer terminates with X or Q equal to 0, or an error is detected on the serial or parallel highway, CHECK CONDITION status (2) will be returned any time the transfer length is not satisfied. In this case, the REQUEST SENSE command can be issued to determine the cause of termination, and the number of bytes successfully transferred. Please refer to the 3.3 for the format of the data returned, and a brief discussion of errors. For more complex errors, particularly those detected on the serial highway, the main status register and serial status register should be examined. It was noted that bytes 4 through 6 indicate the number of CAMAC words that failed to be transmitted between the controller and the CAMAC system. It is stressed that this value is in terms of CAMAC WORDS (16 or 24 bit) instead of bytes. (In the case of CAMAC writes, the word incurring the error will be counted as transferred.)

 Byte 8 of the sense data contains the following flags:

 3. TIMOS and SNEX  Indicate that Serial Time-Out occurred before
     serial transmitter began its operation. Normally, it
     indicates that a receiver did not have sync in Bit
     Mode and the transmitter was therefore prevented
     from starting.

Other status register bits may also be set along with SNEX because of garbage bytes occurring on the highway.  SNEX, however, indicates a positive indication that no CAMAC command was executed.
 
 Byte 14 of the sense data returns the final Crate number in the 7 most significant bits, and the value of N16 in the least significant bit. Byte 15 returns N8-N1 in the hi-order nibble, and A8 - A1 in the low-order nibble. In the case of an Address Scan terminated  by an error, the CAMAC address will have been bumped.
 

4.4.5 Commands to Crate 0

 Commands to CAMAC crate 0 are used for system wide purposes such as enabling/disabling asynchronous LAM's, and polling for LAM’s. An F(26) command to serial or parallel crate 0 will enable LAM's from the respective highway to signal the host asynchronously, as described in the following section . An F(24) command disables them. Recall that the host adapter must have target capability for the AEN procedure to work. An F(0) command to parallel crate 0 will result in a branch GL operation, and either 2 or 4 bytes will be sent to the host, using the byte order selected for data transfers. When a demand is received on the parallel highway, the Branch Demand Sequencer is set. It is reset by a read of parallel crate 0 or by the AEN procedure to be described. In addition, the BDMD bit in the main status register is a live indicator of the state of the parallel highway D line.

 An F(0) command to serial crate 0 will transmit the entire contents of the serial demand stack to the host. In this case, the number of bytes to be sent is not known to the host in advance, but can be determined by the host software. In the case of a serial F(0) LAM poll, the high-order byte of each word in the demand stack is sent first, regardless of the strap-selected byte order. The 16 bits of the Serial Demand Stack word have the following significance: 

5.0 Asynchronous Event Notification

 If LAMs are enabled as described above, and a LAM arises in an enabled CAMAC module, the Model 411S will become a temporary Initiator and will inform the host at the next opportunity-using the SCSI-2 AEN procedure. It will arbitrate for the bus, select the host SCSI adapter, and send the IDENTIFY message followed by the SCSI SEND command. The host adapter must have been programmed to execute the proper Target mode phases. The SEND command instructs the Target (the host adapter) to transfer data from the Initiator (the Model 411S). The data transmitted is the same, as described above, for LAM polls.

6.0  SCSI Messages

 The Model 411S responds to the following SCSI messages:

       IDENTIFY
       ABORT
       BUS DEVICE RESET
       INITIATOR DETECTED ERROR
       MESSAGE PARITY ERROR
       MESSAGE REJECT
       NO OPERATION
       SYNCHRONOUS DATA TRANSFER REQUEST

 The IDENTIFY message is the SCSI-2 method of selecting the Logical Unit within a target. If a non-zero Logical Unit is specified in the IDENTIFY MESSAGE, the ensuing command will fail. The IDENTIFY message is one byte long, as follows:

 The ABORT message interrupts the currently executing command, and the Controller enters the BUS FREE phase. The BUS DEVICE RESET message causes a hardware reset of the Controller. A Dataway Z is generated, and the UNIT ATTENTION condition is set. LAMs are disabled, and Dataway Inhibit asserted. If synchronous transfers were in effect, the Controller reverts to asynchronous mode.

 The INITIATOR DETECTED ERROR message causes the Controller to issue the RESTORE POINTERS message, and then to retry the Data Phase of the current command. The MESSAGE PARITY ERROR message causes the Controller to resend the previous message. The MESSAGE REJECT message causes the Controller to perform an "unexpected disconnect". This should not occur due to the limited and well defined message repertoire of the Model 411S.

 The SYNCHRONOUS TRANSFER REQUEST message causes the Model 411S to prepare to use synchronous transfers in future data phases and to return a similar message confirming the parameters it will use. Synchronous transfers provide a speed improvement during SCSI Data Phases by eliminating the round-trip propagation delay associated with the REQ/ACK handshake. This message is 5 bytes long, as follows: 

 The Model 411S generates the following SCSI messages under the appropriate circumstances. The host must be prepared to process them.  The second two messages are responses to host messages, and their generation can therefore be prevented.

          COMMAND COMPLETE
          RESTORE POINTERS
          SYNCHRONOUS DATA TRANSFER REQUEST

The COMMAND COMPLETE message is one byte transmitted in MESSAGE IN phase at the completion of every command-after the STATUS Phase. Since the Model 411S does not support linked commands, this message is always NULL. The RESTORE POINTERS message tells the host to reset its data buffer pointer to its initial value, since the Target intends to retry the data transfer phase of the current command from the beginning. The SYNCHRONOUS DATA TRANSFER REQUEST message is only generated in response to a similar message from the host. The Model 411S will not initiate synchronous transfers. All AEN transfers use asynchronous mode.

 Since some operating systems are not prepared to accept the MESSAGE REJECT or MESSAGE PARITY ERROR messages, the Model 411S does not generate either. In the event that it receives corrupted or invalid message, it merely disconnects from the bus. This "unexpected disconnect" informs the host that an error has occurred; however, the response to an invalid IDENTIFY message is sent in Status Phase, as noted earlier.

 During Asynchronous Event Notification, the Model 411S generates the IDENTIFY message to convey the host's Logical Unit Number(which is expected to be zero). It further expects the host to send the COMMAND COMPLETE message after sending the status byte.

7.0  Serial Highway Operation

7.1  Installation and Hardware Settings

 If the Serial Highway Option is installed, either a Bit-Serial or Byte-Serial Highway can be connected to the connectors labeled “D-input” and “D-output”.  A number of switches will be found on the Serial Highway Driver board, which occupies the lower most slot in the backplane. These switches can be set through an access door in the front panel of the Serial Highway Driver.  They control the following operation parameters. The selections made at shipment should be as listed in the second column. 

7.1.1 Serial Time-Out

 The serial time-out circuits operate in the terms of message bytes instead of real time.  This allows the timer to be set for the particular serial highway configuration independent of the system clock rate. To avoid spurious time-out indications, the settings must exceed the maximum number of bytes that can be received under normal circumstances(between the time that a Serial CAMAC operation is commanded and the final byte of the reply received). Factors contributing to this number are the following: