Specifications

Data Structures

1.7 Channel Request Block (CRB)

The activity of each controller in a conﬁguration is described in a channel request

block (CRB). This data structure contains pointers to the wait queue of drivers

ready to gain access to a device through the controller. The CRB also stores the

entry points to the driver’s interrupt service routines and the unit or controller

initialization routine.

The channel request block is illustrated in Figure 1–9 and described in

Table 1–8.

Figure 1–9 Channel Request Block (CRB)

CRB$L_FQFL 0

CRB$L_FQBL 4

CRB$W_SIZE*CRB$B_TYPE*CRB$B_FLCK 8

CRB$L_FPC 12

CRB$L_FR3 16

CRB$L_FR4 20

CRB$L_WQFL* 24

CRB$L_WQBL* 28

CRB$B_TT_TYPE*Unused 32

CRB$W_REFC*CRB$B_MASK*CRB$B_UNIT_BRK* 36

CRB$L_AUXSTRUC 40

CRB$L_TIMELINK* 44

CRB$L_DUETIME* 48

CRB$L_TOUTROUT* 52

CRB$L_LINK* 56

CRB$L_DLCK* 60

CRB$L_BUGCHECK* 64

CRB$L_RTINTD* (12 bytes) 68

CRB$L_INTD* (40 bytes) 80

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