IBM 1 Series - DPC Adapter Operational Characteristics; Output Sequence

DPC Adapter Operational Characteristics
Output Sequence
6-8
GA34-0033
The DPC adapter performs three types of information or status transfers:
output, input, and interrupt-service sequences.
There are no timing restrictions inherent in the interface architecture and,
as such, the interface is called asynchronous. This means that the response
from a given I/O device triggers the next sequential action rather than a
specified timing condition. (Time-out indications for error detection are
not excluded.)
Figure 6-3 is a timing diagram for a typical output sequence.
An output sequence is executed as follows:
1. Function, modifier, device address bits, and data are placed on their
appropriate lines.
2. The ‘I/O active’ tag is skewed (at least 200 nanoseconds) and
activated on the interface.
3. Upon recognition of an address compare and ‘I/O active,’ the device
raises the ‘select response’ tag. Once raised, this tag must be held
active at least until the fall of the ‘I/O active’ tag. ‘Condition code in’
must be active until ‘strobe’ becomes active or until ‘I/O active’
becomes inactive for the duration of the ‘select response’ tag.
4. ‘Strobe’ is activated and dropped.
Note: If the DPC adapter feature is configured without the parity
option and a parity error is detected between the processor I/O
channel and the feature, ‘strobe’ is not activated except during the
Device Reset command.
The ‘I/O active’ tag is deactivated.
Upon recognition of the absence of the ‘I/O active tag,’ the device
drops ‘select response’ and ‘condition code in.’
7. The function, function modifier, device address, and data buses are
deactivated.
Output sequence
Control lines _— +)
and
data
bus
out
>200
ns
I/O active _
Strobe >0 <1.5ys
>200 | >50 ns
Strobe (device) <
/ >100 ns
<1.5 pus S va
Select response > 0 _
Condition code in
Figure 6-3. Output sequence timing diagram