IBM 1 Series - Page 85

2-74
GA34-0033
Direction logic for bidirectional address and data lines is provided on the
feature so that its operation is transparent to the outboard I/O
attachments. In the absence of any activity on the channel, the
bidirectional buses (data bus and address bus) are shut off. The repower
feature inhibits the outboard signal lines from affecting the availability of
inboard devices when the outboard attachment or card file is powered
down. ‘Data strobe’ is not propagated through the repower card unless
either the ‘address gate return’ tag or the ‘service gate return’ tag coming
from an outboard file is active.
The feature has a TTL-level compatible hysteresis receiver for the
outboard ‘power-on reset.’ The receiver has a maximum current of 100
microamperes, which the outboard attachment or card file is required to
sink at 0.45 V (most positive down level) when powered down or actively
signalling ‘power-on reset.’
The pin assignments for the repower feature are listed in Figure 2-33. The
top-card connectors (TCCs) are standard IBM connectors, and receive
standard I/O channel cables. For reference purposes, TCC pins WO2,
X02, YO2, and ZO2 correspond to cable pins DO2, JO2, PO2, and U02,
respectively. Top card connectors W, X, Y, and % correspond to cables 1,
2, 3, and 4, respectively. Therefore, when facing a repower feature that is
plugged into an I/O socket, the W-connector is at the top and would
receive cable 1 (see Figure 2-32).
Top-card connector pins W26, W31, X26, X31, Y26, Y31, Z26, and Z31
are grounds to receive the special grounds in the [/O channel cables. Pins
W08, X08, YO8, and Z08 are also grounded pins, corresponding to the
normal grounds supplied on an I/O socket. There are no connections to
pins W0O3, X03, YO3, and 703. These pins correspond to the normal
+5-volt dc pins on an I/O socket (D03, JO3, PO3, and U0O3).