Start of change

I/O Instructions

As mentioned earlier, ESA/390, ESA/XC, z/Architecture®, and z/XC architectures and System/370 architecture support different sets of I/O instructions. When you use I/O instructions in your program, you must make sure you use the I/O instructions appropriate for the mode of virtual machine in which the program is to run. An operation exception occurs in your program if it issues the wrong mode of I/O instruction (a System/370 I/O instruction in an ESA, XC, or XA virtual machine). Most CMS applications that are written by using System/370 I/O instructions can run in an ESA, XA, or ESA/XC (but not z/XC) virtual machine. You must use the CP SET 370ACCOM ON command or the CMS SET CMS370AC ON command.

Information on the CP SET 370ACCOM command is available in another publication. See the z/VM: CP Commands and Utilities Reference.

Information on how to run your 370-only CMS applications in an ESA XA or XC virtual machine is available in another publication. See the z/VM: CP Programming Services.

Information on the CMS SET CMS370AC ON command is available in another publication. See the z/VM: CMS Commands and Utilities Reference.

ESA/XC and ESA/390 architectures maintain compatibility to System/370 in the areas of CCWs, IDAWs, and channel programs. However, you must be careful when you replace System/370 I/O instructions with the ESA/XC or ESA/390 counterparts; System/370 and ESA/390 or ESA/XC condition codes do not necessarily mean the same thing. (For example, TIO condition codes need to be handled differently than TSCH condition codes.)

Table 1 lists the I/O instructions in each architecture.

Table 1. I/O Commands of several architectures
ESA/390, ESA/XC, z/Architecture, and z/XC I/O Instructions Mnemonic System/370 I/O Instructions Mnemonic
CLEAR SUBCHANNEL CSCH CLEAR CHANNEL CLRCH
HALT SUBCHANNEL HSCH CLEAR I/O CLRIO
MODIFY SUBCHANNEL MSCH HALT DEVICE HDV
RESET CHANNEL PATH RCHP HALT I/O HIO
RESUME SUBCHANNEL RSCH RESUME I/O RIO
SET ADDRESS LIMIT SAL START I/O SIO
SET CHANNEL MONITOR SCHM START I/O FAST RELEASE SIOF
START SUBCHANNEL SSCH STORE CHANNEL ID STIDC
STORE CHANNEL PATH STATUS STCPS TEST CHANNEL TCH
STORE CHANNEL REPORT WORD STCRW TEST I/O TIO
STORE SUBCHANNEL STSCH    
TEST PENDING INTERRUPTION TPI    
TEST SUBCHANNEL TSCH    

Complete information on these and other assembler language instructions are available in another publication. See z/VM: ESA/XC Principles of Operation.

End of change