Eprom Circuit Pack; General Description; Replacing Eprom Integrated Circuits - Northern Telecom BCS35 Replacement Manual

EPROM circuit pack

General description

This circuit pack, in slot 2 of the A and B chassis, stores the main program
for DPP operation. It contains 16 Kilobytes (Kbytes) of EPROM and 48
Kbytes of RAM. At power up, the EPROM Boot and Monitor programs
automatically download the main program from disk to RAM.
A power regulator IC on this circuit pack reduces the nominal +8.5 V dc
provided by the power supply to a regulated +5 V dc for circuit assembly
operation.
There are jumper settings on the EPROM. See Tables 3–1, 3–2, and 3–3.
Figure 3–1 shows the jumper locations and circuit pack layout.

Replacing EPROM integrated circuits

The DPP contains Erasable Programmable Read Only Memory (EPROM)
firmware routines. EPROM Integrated Circuits (ICs) contain operational
programming for some DPP system functions. The EPROM's fixed
memory is factory programmed with necessary control instructions. After
installation in the DPP, the EPROM always responds in the same manner.
You may replace an EPROM IC with another EPROM IC having the same
set of programmed instructions, for example when an EPROM malfunctions
or fails. However, to change the way the DPP functions, install an EPROM
IC with different programmed instructions.
See Procedure 3–1 for removal, installation, and handling precautions when
changing DPP EPROM ICs. There are two methods for changing EPROM
ICs. One method is to replace the EPROM ICs and the PEC/rel label on the
circuit pack. Another method is to replace the entire circuit pack.
Note: 1 If replacing EPROM ICs, check the reference number on the circuit
pack diagram to make sure the right EPROM type is being used.
DPP Card Replacement Guide BCS35 and up
17