page of GC20-1807-7 As Updated April 1, 1981 by TNL GN25-0829 BDEVTMCD Terminal code bits defining the type of console and
- or -the translate table the console is using. BDEVTMCD is
NICTMCD for a local virtual console; NICTMCD for a remote 3270 virtual console r-- -----------------------------------------------------, I Byte 0 Byte 1 Byte 2 Byte 3 I I I I VDEVTYPC VDEVTYPE VDEVSTAT VDEVFLAG 1 L--- VDEVTYPC virtual device type class VDEVTYPE virtual device type VDEVSTAT virtual device status VDEVFLAG Virtual device flags
Byte 0 Byte 1 Byte 2
,
Byte 3 I --------------------------------------1 BDEVTYPC BDEVTYPE - or - NICDTYPE BDEVMDL - or -
NICHDL BDEVFTB I - or - 1 BDEVLLEN I - or - 1 NICLLEN I ___________________________________________________J RDEVTYPC Real device type class RDEVTYPE Real device type RDEVMDL Real device model number
RD EVFTR Real device feature code for a device other than a virtual
console RDEVLLEN Current device line length for a local virtual console NICDTYPE Real device type for a remote 3270 virtual console
NICMDL Real device model number for a remote 3270 virtual console
NICLLEN Current device line length for a remote virtual console
Part 2. Control Program (CP) 193

April 1,1981
The following chart lists the DIAGNOSE Code X'24', the meaning
registers where data is returned • cond ition
of each
codes CP can return
condition code, and .-- I , This register
contains information , If the condition
code equals Ry Ry+i2 Comments o x x
2 x x
3 X INormal completion I Undefined IThe virtual device
lexists but is not
lassociated with a Ireal device I Invalid device
laddress or the Ivirtual device Idoes not exist
lThe Ex register contains information only when DIAGNOSE Code X'24' specifies a virtual console whose address in unknown.
2If Ry is register 15, CP returns only virtual device infor­
mation: no information is returned in register Ry+1. DIAGNOSE Code X'28' -- Channel Program
Modification
,
for
the DIAGNOSE Code X'28' allows a virtual machine to correctly execute some
channel proqrams modified after the Start I/O (SIO) instruction is
issued and before the input/output operation is completed. The channel
command word (CCW) modifications allowed are: • A Transfer in Channel (TIC) CCW modified to a No Operation (NOP) CCW • A TIC CCW modified to point to a new list of CCis • A NOP modified to a TIC CCW When a virtual machine modifies a TIC CCW, it is modifying a virtual
channel proqram. CP has already translated that channel program and is
waiting to execute the real CCws. The DIAGNOSE instruction, with Code X'28', must be issued to inform CP of the change in the virtual channel
program, so that CP can make the corresponding change to the real CCW before it is executed. In addition, when a NOP CCW is modified to point
to a new list of CCWs, CP translates the new CCWs. To be sure that the DIAGNOSE instruction is recognized in time to
update the real CCW chain, the virtual machine issuing the DIAGNOSE instruction should have a high favored execution value and a low
dispatching priority value. The CP SET command should be issued: SET FAVORED xx SET PRIORITY nn
194 IBM VM/370 SYstem Programmer's Guide