ICL 1900 Series Computers

Order Codes 15x

Octal Order Code	Nmenonic	Execution
150	SUSBY X N(M)	Suspend if Busy The SUSBY instruction will cause EXECutive to test whether the unit specified is busy. If it is busy, the program member giving the order will be suspended until such time as the unit is free; the program member may then continue. With Direct Access devices the program member is suspended while any transfer specifying the same file number is incomplete. There are two formats:- X = Unit Number or File Number (0-7). N(M) = Type Number of Peripheral. Least significant 6 bits of X contain the Unit Number or File Number (0-63). N(M) = 256 + Type Number of Peripheral. C is not used and will be left clear. V is not used and remains unchanged. Modification This statement has an M field. When modified, the least significant 15 bits of N + M are taken as the operand. In the extended data mode, the least significant 22 bits of N + M are taken as the operand.
151	REL X N(M)	Release Peripheral The REL instruction causes the unit specified to be released from the program and made available for allocating to that or any other program. The unit is also disengaged. This instruction cannot be used for a magnetic tape unit or file storage device. Any transfer of information which is in progress is completed before the unit is released and the program is suspended pending completion. On completion of the transfer, EXECutive releases the peripheral and records the release on the console typewriter; the program then continues automatically. There are two formats:- X = Unit Number or File Number (0-7). N(M) = Type Number of Peripheral. Least significant 6 bits of X contain the Unit Number or File Number (0-63). N(M) = 256 + Type Number of Peripheral. C is not used and will be left clear. V is not used and remains unchanged. Modification This statement has an M field. When modified, the least significant 15 bits of N + M are taken as the operand. In the extended data mode, the least significant 22 bits of N + M are taken as the operand.
152	DIS X N(M)	Disengage Peripheral The specified peripheral is disengaged, so that it cannot be used in a subsequent transfer until the operator has re-engaged it by pressing the ALLOCATE button. The peripheral remains allotted to the program. Before disengaging the unit EXECutive checks that it is not busy. If the unit is busy EXECutive suspends the program, removing the suspension and proceeding with the instruction when the peripheral is not busy. If an attempt is made to initiate a transfer using a peripheral after it has been disengaged and before it has been re-engaged, the program is suspended, and EXECutive types a message on the typewriter console to notify the operator of the situation. There are two formats:- X = Unit Number or File Number (0-7). N(M) = Type Number of Peripheral. Least significant 6 bits of X contain the Unit Number or File Number (0-63). N(M) = 256 + Type Number of Peripheral. C is not used and will be left clear. V is not used and remains unchanged. Modification This statement has an M field. When modified, the least significant 15 bits of N + M are taken as the operand. In the extended data mode, the least significant 22 bits of N + M are taken as the operand.
153		Unassigned
154	CONT X N(M)	Read in More Program The CONT instruction causes the program to be suspended immediately. EXECutive then reads binary program (which must be in standard format, but must not include a request block) from the specified peripheral into the program's area, the locations overwritten being determined by the data blocks read. The transfer terminates when an entry block is read. The action taken on completion of the loading will depend on the type of entry block read. Usually this will be of type 4, which will cause the program to continue with the instruction in the location following that which contained the CONT instruction (either or both of these locations may have been overwritten by the program just read in). There are two formats:- X = Unit Number or File Number (0-7). N(M) = Type Number of Peripheral. Least significant 6 bits of X contain the Unit Number or File Number (0-63). N(M) = 256 + Type Number of Peripheral. C is not used and will be left clear. V is not used and remains unchanged. Modification This statement has an M field. When modified, the least significant 15 bits of N + M are taken as the operand. In the extended data mode, the least significant 22 bits of N + M are taken as the operand.
155	SUSDP X N(M)	Suspend and Dump The SUSDP instruction causes the program to be suspended immediately. EXECutive then dumps the whole of the program area, in binary program form, onto the specified peripheral unit. The dump of the program area is preceded by a request block and terminated by a type 3 (suspend) entry block. On completion of the dumping, the program resumes with the instruction in the location following that which contained the SUSDP instruction. There are two formats:- X = Unit Number or File Number (0-7). N(M) = Type Number of Peripheral. Least significant 6 bits of X contain the Unit Number or File Number (0-63). N(M) = 256 + Type Number of Peripheral. C is not used and will be left clear. V is not used and remains unchanged. Modification This statement has an M field. When modified, the least significant 15 bits of N + M are taken as the operand. In the extended data mode, the least significant 22 bits of N + M are taken as the operand.
156	ALLOT X N(M)	Allot Peripheral Basic Peripherals, the Interrogating Typewriter Facility, the Multiplexor and the Digital Incremental Plotter The ALLOT instruction requests allocation of a peripheral during the running of a program. This allows for more efficient use of peripherals as they need not be allotted to a program until they are required. When used with suitable Executives, this instruction can also specify properties required of the peripheral (except for the interrogating typewriter facility and the multiplexor). Reply information to the ALLOT instruction is set into word 9 of the program. If 512 is added to an operand of format 2 below, then assigning of the peripheral is inhibited, but reply information is still set into word 9. This provides a means of ascertaining whether a basic peripheral is assigned to the program without the risk of causing an assignation. Other Peripherals Peripherals other than those specified in 1 above cannot be allotted by the ALLOT instruction, but the instruction will nevertheless set reply information into word 9 of the program. With magnetic tapes and cassette tapes the ALLOT instruction can therefore be used to ascertain whether a particular unit has been assigned to the program, and if so, its absolute unit number and (with suitable EXECutives) its properties. (Note that the ALLOT instruction cannot serve this purpose on a machine without a console typewriter, as on such machines all peripherals are assigned to the program: an affirmative reply would therefore be given whether a tape file had been opened or not.) With direct access devices the ALLOT instruction can be used to ascertain whether a particular file number is in use by a program. There are two formats:- X = Unit Number or File Number (0-7). N(M) = Type Number of Peripheral. Least significant 6 bits of X contain the Unit Number or File Number (0-63). N(M) = 256 + Type Number of Peripheral. C is not used and will be left clear. V is not used and remains unchanged. Modification This statement has an M field. When modified, the least significant 15 bits of N + M are taken as the operand. In the extended data mode, the least significant 22 bits of N + M are taken as the operand.
157	PERI X N(M)	Initiate Peripheral Action The PERI instruction causes a program entry to EXECutive. EXECutive, dependent on the contents of the control area, will initiate the peripheral operation after checking that the specified peripheral is free. There are two formats:- X = Unit Number or File Number (0-7). N(M) = Type Number of Peripheral. Least significant 6 bits of X contain the Unit Number or File Number (0-63). N(M) = 256 + Type Number of Peripheral. C is not used and will be left clear. V is not used and remains unchanged. Modification This statement has an M field. When modified, the least significant 15 bits of N + M are taken as the operand. In the extended data mode, the least significant 22 bits of N + M are taken as the operand.