IBM Professional Series User Manual page 361

value, notifies the 3270 display system that the next byte in
the data stream is an attribute character. For a description
of how the 3270 display system uses attribute characters,
and to determine the values to specify for attribute
characters and the start-field order, see the IBM 3270
Information Display System Component Description.
After processing DIAGNOSE code X'58', CP sets a
condition code.
If
the operation was successful - that is, no
110 errors occurred - CP sets a condition code of zero.
If
an
110 error occurred, CP sets a condition code of one.
If
an I/O error occurred, the application program can check
the I/O status and the error type by:
• Issuing a TEST I/O (TIO) instruction
• Examining the returned condition code
Examining the virtual CSW
The returned condition codes and CSW status are the
standard condition codes and status defined in the IBM
Systeml370 Principles of Operation.
You must also make sure that the interrupt for the virtual
device is enabled by setting the appropriate bit and channel
mask in the PSW. For example, if the virtual address of your
console is OIF, bit 0 in the channel mask must be set to one
(that is, bit 0 must be on). This may be the case if you are
loading programs in the VM/PC CMS transient area.
Full Screen Mode
DIAGNOSE X'58' provides a means by which a virtual
machine may share, with CP, control of a 3270 display
station. Two CCW operations, X'29' and X'2A', in addition
to performing the requested I/O, notify CP that the display
station is operating under the control of the virtual machine.
CCW code X'29' performs a WRITE, or ERASE/WRITE,
operation, depending on the value of the control field. For
the WRITE, and ERASE/WRITE, the virtual machine must
provide appropriate control information beginning with the
A-22
VM/PC Users
Guide