IBM 1 Series - Power Supply Electrical Characteristics; Processor I;O Channel Physical Characteristics; Signal Pin and Cable Assignments

Circuit Module Overvoltage
All circuit modules must have an overvoltage rating for voltage supplied of
40 percent over nominal.
Power Supply Electrical Characteristics
The power supplies for the processor and I/O expansion units provide five
regulated dc output voltages: +5.0, +8.5, +12.0, —5.0, and —12.0 volts.
Both supplies contain overvoltage, undervoltage, and overcurrent
protection. Should overvoltage or undervoltage occur, the condition
initiates a power supply shutdown sequence. (See IBM Series/1
Configurator,
GA34-0042, for use of the Communications Power feature,
#2010.)
Sequencing Requirements
The ‘power on reset’ signal is provided to ensure the state of the logic
during power on and off. The signal is TTL-compatible. A logical 1 (up)
level is between +2.6 V and +5.5 V; a logical 0 (down) level is between
0.0 V and +0.4 V. The ‘power on reset’ signal starts at the TTL down
level. When the +5 V, —5 V, and +8.5 V are within operational limits,
this signal goes to the TTL up level after a 500-millisecond delay. Should
any of the three voltages go approximately 3 percent below their minimum
tolerances, this signal goes to the TTL down level.
Logic Voltage Sequencing
If a user incorporates a technology such that voltage sequencing must
occur within a given period of time (>350 ms), the following method can
be used: Assume that, for substrate biasing purposes, V,=—5.0 V and
V,=t8.5 V; if V, is more positive than —-3.5 V, V, must not remain
above +5.0 V for more than 500 ms. Although no true sequencing occurs,
after approximately 350 ms the power supply circuitry checks to see that
the voltages are at an operational level. If they are not, the supply shuts
down; otherwise, the sequencing is met and the technology is protected.
Processor I/O Channel Physical Characteristics
This section describes I/O pin and cable assignments for all standard
channel signals, voltages, and identifies special reserved lines. It also
provides basic data for the basic physical components of the channel.
Signal Pin and Cable Assignments
Figure 2-28 defines the signal lines and shows their corresponding cable
and I/O pin assignments. Figure 2-29 defines the voltage/ground/special
pin assignments and compares a typical I/O slot position to the A-slot
position. The corresponding I/O cable pin assignments are also given in
this figure. When connecting to an I/O expansion unit, four standard I/O
channel cables must be used to obtain all signal lines. These cables leave
the 4955 processor via the A-socket position on the board or via a
repower card contained on the board, depending on the configuration. The
4952 and 4953 processors can only be cabled out via a repower feature. In
an I/O expansion unit, the A-socket is restricted for use as the entry point
for the I/O channel cables.
2-66 GA34-0033