The address to which centrol is
returned upon coapletion of operation to be
the
In addition, the IOBLOK contains status
flags that indicate the current state of
the operation (such as, whether or not an
error has occurred, if an errcr recovery (ERP) is in and the
condition returned fro. the 510) and the CSW associated with the interrupt that
signals the end of the operation. Since IOBLOKS are queued off various I/O control
tlocks, they also contain forward and
backward queue pOinters. DMKIOS builds in thea the real device address of the unit on
which the operation is started.
In general, the IOBLOK representing a
given operation progresses through the
system by being queued, in turn, from device, control unit, and channel blocks
until a path is at last free to the device.
A 510 is then issued. After the operation
is complete, the IOBLOK is dequeued fro.
the RDEVBLOK and stacked on a queue maintained in the dispatcher, D!KDSP. Each tiae the dispatcher is entered, the entries
on the queue are unstacked and control is
passed to the point sFecified in the
Interrupt Return Address (IOEIBA). After
I/e contrel stacks the ICELCK for the given task, it attempts to restart all of the
components that have been freed by the completion of the operation. NEiWOBK INTERFACE CONTBOL fLOCK There is one Network Interface Centrol Elock (NICBLOK) for each defined 370% and
each resource attached to a 3270 bisynchronous line. The NICELOK provides
the correspondence between the line or
device address and the Fhysical resource
connected to that line. This block not
only defines the identity of the terminal type, line, or control unit but it also
contains flags and status information pertaining to that resource. If the
defined resource is a remote 3270 component, the NICELOK ccntains the current
line coordinates
l polling and selection
characters information as veIl.
The remainder of this secticn describes
the real I/O control blocks.
80 IBM VM/370 Data Areas and Control Block Logic
RCHELCK RCHBlOK contains status and tYFe information for the sFecified channel. The linkage to I/O tasks oFerated on by that channel and to the contrel units attached tc that channel
is also maintained. The ARIOCH field of the points to the first RCHELOK, which is
generated in contiguous storage.
o
8 10 18 20 Hexadecimal
tisplacement
------------ 0 2
4
5
6
8 C 10 11
12
13
14
18 1C 20 RCHADD I RCHlOCK R*1 R*2 BCHQCNT RCHFIOB RCHLICB R*3 I R*4 I R*5 I R*6 RCHSTIDC RCHRSTQ RCHOPER RCHCUTBL Field
Name BCHADD DS RCHlOCK 1)S RCHSTIT DS RCHBUSY EQU RCHSCED EQU RCHDED EQU RCHTYPE DS RCHSEl EQU RCHBMX EQU RCHBPX EQU RCH370 EQU RCHQCNT DS RCHFIOB DS RCHlIOB DS RCHDTCK DS RCHCCCK DS RCHIFCC DS RCHCHCK DS RCHSTIDC DS RCHRSTQ DS RCHOPER DS RCHCUTBl DS RCH5IZE EQU (Variable Length)
1H
1H 1X in RCHSTAT --X'SO,-- X'40' X'01' 1X in RCHTYPE -X'SO,-- X'40' X'20' X'01' 1H
1F
1F 1X 1X 1X 1X 1F
1F
1F
32H
Field Description, Contents, Meaning Channel address Channel lock
R*1 Channel status
R*2
R*3
R*4
R*5
R*6 Channel tusy IOE scheduled on channel Channel dedicated Channel type
Selector channel Elock multi Flexer channel Eyte multiplexer channel 5/37C type channel (5/370 I/C instructicn
sUFPort)
Number of ICBLOKs queued off channel Pointer to first IOBLOK queued
Pointer to last IOBLOK queued Channel data check count Channel control check count
Interface centrol check ceunt Channel chaining check count
Result of STIDC instruction issued
at CP initialization; if cc = 3, the
content is X'FFFFFFFF' Address of channel to be restarted IOELCK operational on channel time Control units attached - RCUSTART index
(The index values must be multiplied
by 8 and added to the beginning of the RtEVELOK table (ARIODV).) (*-RCHBlOK)/8 RCHELOK size in doublewords (X'OD') Section 1. CP Data Areas and Ccntrol Elecks 81
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