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9 8 ___ User Manual for Microboard Computer Development System CDP18S693 & CDP18S694
fig H2—Block diagram of PROM programmer module group-selection logic.
address, data, and control signals at ground after each
operation so that PR O M ’s can be inserted and
removed without having power applied to them. The
I/O ports and all logic circuits on the board are
continuously powered by the +5-volt Vcc supply from
the MCDS. A power-up reset circuit is included to
assure that no unwanted voltages will be applied to a
PROM should one accidentally be in a socket when the
MCDS is turned on.
A selection switch Sl selects either the 1702 or the
CDP18U42 configurations for socket 1. The switch
generates a signal to EF1 ofthe CPU which is tested by
the software at the start of an operation to make sure
the switch is in the correct position before proceeding.
If some other piece of user-installed hardware, not
covered by a group select, is connected to EF1, some
alternative arrangement will have to be made.
Three LED status indicators are provided on the
edge of the Module. The one labeled PROG will be ON
when a PROM is actually being programmed and
OFF at other times. The one labeled 5 V indicates that
+5 V is being applied to the PROM ’s. This indicator is
controlled by power switch S2. PROM ’s should not be
inserted or removed when this LED is ON. The third
LED, labeled PROG PWR, indicates thattheexternal
programming voltage power supply is ON and
connected through to the drivers circuits on the
Module.
Schematics, Layout Diagram, and
Parts List
Figs. H3, H4, H5,andH 6containtheschem aticand
logic diagrams for the PROM Programmer Module.
Fig. H7 is the layout diagram and is followed by the
parts list.