Data Retention For Rtc And Sram; Front Panel Buttons And Led Ports - PEP VM162 User Manual

Chapter 2 Functional Description

2.7.6 Data Retention for RTC and SRAM

Short term data retention for RTC and SRAM is gained with two Gold-Caps, each with a value of 0.22
Farad. In contrast to Lithium cells, Gold-Caps do not require servicing. This short term backup is inten-
ded for short power failures or for reconfiguring systems. An empty Gold-Cap needs approximately
three hours to charge up, with backup times dependant on the temperature, memory size and memory
manufacturer tolerances. A well charged Gold-Cap provides a minimum of 10 hours backup time.
Laboratory tests at PEP indicate a typical backup time of 1 week for both 256kB and 1MByte SRAM
plus RTC (typical onboard backup current is 2 µA).
Long term data retention is made via the VMEbus 5V Stby line. With respect to the VM162/VM172, this
voltage can drop to 2.5V, with the typical current via the 5V Stby being 30µA at 3V.
Notes: The VM162/VM172 board can be removed from the system and plugged in again without lo-
sing any information. Data retention switches from the VME 5V Stby to the on-board Gold-Caps au-
tomatically.
The on-board Gold-Caps are continuously reloaded via the 5V Stby line. The 5V Stby current is typically
7mA for a few minutes when the Gold-Caps are at the beginning of the loading phase (fully dischaged).

2.7.7 Front Panel Buttons and LED Ports

Figure 2.1 LED Port and Button Location
2.7.7.1 RESET/ABORT Button
A RESET button is fitted to the front panel to avoid false operation. The RESET button triggers the on-
board system reset generator, as well as the VME if jumper J2 is set.
Together with the RESET button, an ABORT button is also fitted to the front panel. The ABORT button
generates a level 7 IRQ (non-maskable interrupt) which is used for debugging purposes. In this case, bit
1 of the Board Control/Status Register is not set (remains '0').
2.7.7.2 LED Port
The front panel LED port consists of three LEDs with the following functions:
Red LED
Yellow LED
Green LED
The green LED is free to be used by the customer. It is set by the software during startup when the
68EN360 is initialized.
Juli 23, 1997
Watchdog LED
Yellow
User General Purpose
Green
U
RESET Switch
RST AB
CPU in HALT or RESET status.
Watchdog timer running status.
General purpose, set via Board Control/Status Register.
© PEP Modular Computers
CPU HALT or RESET
Red
W H
ABORT Switch
VM162/VM172
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