BOOTING A REMOTE STATION

DMV II-based networks provide the user program, at the multipoint control station or point-to-point station, with the ability to boot the main CPU at a remote station that has been shut down due to power outage or software malfunction. There are three ways this boot function can be performed:

1. Remote load detect: The control station starts the primary MOP boot procedure for a remote station.

2. Power-on boot: The first poll received after power-up at the remote station causes the DMV 11 at that station to request that the control station start the MOP boot procedure.

3. Invoke primary MOP: The user program at the remote station causes the DMV 11 to request that the control station start the primary MOP boot procedure.

NOTE

Control station is either a multipoint control or point-to-point station that is transmitting (over the link) the boot or requested program to the remote station. Remote station is either a multipoint tri-butary or point-to-point station that is receiving (over the link) the boot or requested program.

NOTE

Power-on boot, remote load detect, and invoke primary MOP are not mutually exclusive. All three features could be used in a particular application.

Primary MOP boot procedures require that the DMVII be switch-configured in the manner specified in this section. The steps taking place at the remote station and over the communications line leading to each of the three primary MOP boot functions are presented in the following sections.

4.7.1 Steps Leading to a Remote Load Detect Boot

The steps taking place at the DMV 11 remote station and its host CPU in response to an enter MOP mode message from the control station are:

1. The DMV 11 NPRs a tight-loop routine into main memory.

2. The DMVll transfers control to the routine through the power fail/restart vector. This rou-tine inactivates the CPU to prevent any intervention during the NPR process.

3. The DMVl1 then sends a primary MOP request program message to the control station. The control station responds in turn with a primary MOP memory load with transfer address mes-sage containing the boot or related program to be loaded into main memory at the remote station.

4. The DMV 11 NPRs that program into main memory, then starts executing the program.

5. At this point the remote station is operating in the manner intended by the down-line loaded program.

The steps occurring over the communications line during a remote load detect boot are:

1. The control station sends an enter MOP mode message to a remote station.

2. The remote station recognizes the address and password in the message, then inactivates its host CPU.

3. The remote station then responds with a primary MOP request program message.

4. The control station responds to this message with a primary MOP memory load with transfer address message containing the boot or related program to be loaded into the host CPU at the remote station.

4.7.2 Steps Leading to a Power-On Boot

When power is restored after a shutdown at a remote station, the DMV 11 performs the same steps used during a remote load detect boot. However, the first two steps performed over the communications line are omitted, and the tributary station responds to the first poll from the control station with an MOP

4.7.3 Steps Leading to an Invoke Primary MOP Boot

This boot operation is initiated when a user at a remote station sets the boot and master clear bits in the DMV 11 initialization register (see Section 3.3.1). The steps taken by the DMV 11 are the same as with a power-on boot.

4.7.4 DMVll Switch Settings for the Boot Functions

At remote stations, in networks supporting the primary MOP boot functions, the switches must be con-figured in a specific way in order to properly perform the boot functions (see Section 2.5 and Table 2-6).

NOTE

The switch setting procedures described below apply only to tributary stations in a multipoint network and one node in a point-to-point network.

The unit number (zero or one) of each DMV 11 must be appropriately set. This number allows the boot program, once it is loaded into the host CPU, to identify the specific DMVll (within the host's floating address space) performing the boot.

NOTE

When primary MOP booting is supported in a net-work, the operating mode of each tributary station eligible for booting must be set in the switches rather than through the mode definition command.

The operating mode of a DMV 11 is specified by setting the mode enable switch to one (OFF) (switch number 1 of the boot enable switch pack), and setting switches numbered 6, 7, and 8 to the required operating mode. The settings for these switches are listed in Table 4-5.

4.7.4.1 Switch Settings for the Power-On Boot Function - To enable the power-on boot function at a remote station, switch number 4 of the boot enable switch pack (power-on boot) must be set to one (OFF). In addition, the tributary address of this station must be set in the DDCMP address switch pack.

4.7.4.2 Switch Settings for the Invoke Primary MOP Boot Function - The DMVl1 switch settings for the invoke primary MOP boot function are the same as those for the power-on boot function. However, the setting of the power-on boot switch has no affect on the invoke primary MOP boot.

An additional feature of the invoke primary MOP boot and remote load detect is that it may allow the tributary address of the remote station to be software assigned instead of switch assigned. This feature is only valid for remote stations that are multipoint tributaries. To use this feature, the following conditions must exist.

• The tributary address/password in the DDCMP address switch pack must be zero.

• The user program at the remote station must have established the tributary using the control command (establish tributary). If the remote station is using the multiple address tributary option. the tributary address used for booting must be the first one established.

NOTE

Invoke primary MOP boot with the software-as-signed tributary address does not work if the power-on boot switch is enabled.

Table 4-5 Mode Switch Settings

Mode Line Network DMC11 Line

Switches Characteristics Configuration Compatibility

6 ⁷ 8

ON ON ON Half-duplex Point-to-point Yes

OFF ON ON Full-duplex Point-to-point Yes

ON OFF ON Half-duplex Point-to-point No

OFF OFF ON Full-duplex Point-to-point No

ON ON OFF Half-duplex Multipoint control N/A

station

OFF ON OFF Full-duplex Multipoint control N/A

station

ON OFF OFF Half-duplex Multipoint tributary NjA

station

OFF OFF OFF Full-duplex Multipoint tributary N/A

station

4.7.4.3 Switch Settings for the Remote Load Detect Boot Function - To enable the remote load detect boot function at a remote tributary station, switch number 5 of the boot enable switch pack (enable remote load detect) must be set to one (OFF). For the remote load detect boot function, the switch-specified tributary address also serves as the password which is contained in the enter MOP mode mes-sage.

When using boot functions in point-to-point networks, the tributary address/password switches can, for security purposes, be set to a unique value since the address of a point-to-point node is always known to be one.