Selective Features For 2715 Model 2 - IBM 2790 Manual

I hexadecimal representation of the number of bytes to print
out (X'00'— X'32'). If no byte count is entered, the 2715
will assume a X'32' count.
Two Processor Switch
This feature allows the 2715 to be attached to the Multi­
plexer Channel of two System/360 Processors. However,
operations may occur with only one of the processors at
any one time. The 2715 Two Processor Switch (TPS) has
three distinct states: neutral; Channel A attached; Channel
B attached. The TPS may be in only one state at a time.
With the TPS in the neutral state, the 2715 is available to
the first channel that selects it. The 2715 will not execute
a 'system reset' from either channel when its TPS is in the
neutral state.
Switching from the Neutral State. In the neutral state, the
TPS will monitor the 'address out', 'select out', and 'bus out
address' on both Channels 1 and 2. If a valid address is
decoded on either of the channels, the 2715 will attach to
that channel upon the detection of 'select out'. Any 'select
out' signal coming from the unattached channel will be
bypassed by the TPS, giving the program a condition-code 3
response to a Start I/O instruction.. The valid address for
attachment to Channel 1 may be different from that of
Channel 2.
Any command, including Reserve, can be used to achieve
initial attachment. After attachment, the Reserve command
is treated exactly as if it were an I/O No-Op command— that
is, immediate CE-DE status is given.
Switching Back to the Neutral State. Only the attached
channel can cause the TPS to return to the neutral state.
This is done by one of two methods:
1. If a 'system reset' is signaled by the attached channel,
the TPS unconditionally returns to the neutral state.
2. If a Release command is issued by the attached
channel to the 2715 and the command is honored,
the TPS will return to the neutral state. To determine
if the 2715 will honor the Release command, the
interface controls will make an immediate check to
see if the 2715 is command-free. If it is not command-
free, it will signal 'busy' as status response to initial
selection and the 2715 will not go to the neutral
state. If the 2715 is command-free, it will signal
'channel end and device end' as a status response to
initial selection and the TPS will return to the
neutral state immediately following the fall of
'operational in'. The Release command should
never be in or at the end of a command chain,
Also, since the CE-DE status presented by the
Release command and accepted by the channel
indicates that the 2715 TPS will unconditionally
return to neutral, command chaining should never
be signaled via the Release command. Once in the
30
neutral state, the TPS is capable of attachment to
the alternate channel, or the channel just released
is eligible to become partitioned.
The TPS may switch to the neutral state through a
'power on reset', which causes the TPS to return uncondition­
ally to the neutral state.

Selective Features for 2715 Model 2

The following selective features can be attached to 2715
Model 2 only:
Dual Communications interface
This feature allows the BSC adapter to operate with an
alternate data-set interface on the common-carrier facility.
The second interface provides switched-network backup of
leased-line facilities.
Synchronous Clock
This feature provides the 2715 Model 2 BSC adapter with
an internal clock for use with those data sets not providing
clocks.
Attach World Trade Modems
This feature provides an interface from the BSC adapter to
the following modem types:
U K GPO— Modem Type 1 Model 5 (see "Note")
600 bps and 1200 bps on leased and switched facilities.
GERM AN P T T (Bundespost)-Modem Type D 1200 S
(GH 2100 Mode/5)
600 bps and 1200 bps on leased and switched facilities.
SW EDISH PTT— Modem Type GH 2002 A , B, and C
A— 600 bps and 1200 bps on switched facilities
B— 600 bps and 1200 bps on leased facilities
C— 600 bps and 1200 bps for in-plant multipoint
JA PAN ESE NTT-Modern Type D T 1203
600 bps and 1200 bps on leased point-to-point facilities.
IBM 3977 Model 1 and 2
Model 1-600 bps and 1200 bps on leased facilities
Model 2— 2000 bps on leased facilities (conforming to
CCITT recommendations M89)
IBM 3976 Model 3
600 bps and 1200 bps on leased and switched
facilities
Note: Support for GPO Datel 1 Model 5 Modem must
include the safety requirement of GPO MEMORANDUM
A2524 (Issue 2), titled: "Memorandum on the Connec­
tion of Privately Owned Equipment to Post Office
Private Circuits."