IBM 1 Series - Data Bus out; Interrupt Service Active; Strobe

Data Bus Out
‘Data bus out’ is an 18-bit outbound bus with 16 bits of data and two
parity bits, odd parity by byte. This bus is used to transfer data and
control information to the I/O devices and is active during write-data or
write-control operations.
During the write-data or write-control operation, ‘data bus out’ is active
from 200 nanoseconds before the rise of the ‘I/O active’ tag until the fall
of the ‘select response’ tag, measured at the output of the DPC adapter
card. During the inactive state, ‘data bus out’ is logically 0, including
parity. When the parity option is not selected, the device uses only the 16
data lines.
Interrupt Service Active
‘Interrupt service active’ is an outbound tag line used to signal an I/O
device that an interrupt-service sequence may now begin. The tag is active
from 200 nanoseconds after ‘device address’ is activated and remains
active until the fali of the ‘select response’ tag, measured at the output of
the DPC adapter card.
Strobe
‘Strobe’ is an outbound line to the I/O device presently being selected
(device address equivalent to the preassigned address of an I/O device)
during an I/O active sequence or an interrupt-service active sequence.
During an I/O active sequence, the device should use ‘strobe’ to register
data on the outbound data transfer or use it to reset data (for example,
Read PI With Reset command) on the inbound data transfer. During an
interrupt-service active sequence, the selected device uses ‘strobe’ to reset
its interrupt request, interrupt information byte (IIB), or interrupt status
byte (ISB).
If a parity error is detected by the processor I/O channel during a
read-data or read-status operation, ‘strobe’ is inactive throughout the
sequence.
If the DPC adapter card is configured without the parity option and a
parity error is detected during a write-data or write-control operation, the
‘strobe line’ is inactive throughout the sequence, except during the
system-defined Device Reset command.
Customer Direct Program Control (DPC) Adapter Feature 6-5