Acorn FileStore E01 User Manual download pdf

NVRAMNVRAM

EEA indexEEA index

FileStore

Description

Hardware

Error codes

NVRAM

Disc format

Accessing

Password

file

E01 vs E01S

Rescuing

Intro

MDFS

Others

Clocks

Bridges

Interfaces

Misc h/w

Testing

Misc info

NVRAM

The FileStore contains a "CMOS RAM", which is a 146818-type fully programmable battery-

backed

memory device.

This device, hereafter referred to as NVRAM (non-volatile RAM), is used for three purposes:

1. To maintain a 'clock' during times when the server is switched off, so that upon power-

up the

server will know what the date and time are.

2. The storage of important system variables, such as the server's station number and the printer

server 'name'.

3. Upon error, the error information is written to the NVRAM. I'm not entirely certain how you

would go about extracting it, but it is there...

The NVRAM requires a continuous supply to keep the data intact. This low-

current supply is

provided by a NiCad battery that outputs 3.6V. The battery is charged by a constant current source

from the +5V rail while the power is on.

When the power goes off, the battery powers the NVRAM and also pulls the

|CE

line high, which

disengages the data and address lines in the device, offering a further reduction in the power required

to maintain the configuration.

The small cylindrical crystal near the battery (in the

E01S

) provides the time base for the NVRAM.

As is common for watches and the like, it operates at 32.768kHz. The variable capacitor near the

crystal allows for fine-tuning and, when the server is undergoing testing, the test point (TP1, by the

NVRAM chip), can be used to ensure that the ticker is running at exactly 1.024kHz.

The NVRAM's address register is mapped in to memory at &FC00, and the data register is mapped in

to memory at &FC04.

NVRAM allocations

Byte(s)

Meaning

0 - 9

Real time clock (internal function provided by the NVRAM chip)

0 Seconds

1 (alarm seconds)

2 Minutes

3 (alarm minutes)

4 Hours

5 (alarm hours)

6 Day of the week (1-

7; Sun=1)

7 Day of the month

8 Month

9 Year (range 0-99)

EEA - FileStore NVRAM allocations

http://angelique/econet/fs/cmos.html

Page 1 of 8 2007/08/23

1 2 3 4 5 6 7 8

Summary of Contents

Page 1 - NVRAMNVRAM

NVRAMNVRAM EEA indexEEA index FileStore Description Hardware Error codes NVRAM Disc format Accessing Password file E01 vs E01S Rescuing Intro MDFS O

Page 2 - Page 2 of 8 2007/08/23

The RS data sheet (March 1997, component ref. 232-2605; stock no. 302-003) claims that the device offers automatic leap year compensation. I wonder wh

Page 3 - Page 3 of 8 2007/08/23

bit 5 not usedbit 6 not usedbit 7 VRT Valid Ram and Time 14 The server station number 15 255 - server station number (used as a check) 16 - 19 Rese

Page 4 - Default values

Default values If the NVRAM is detected to be invalid, then defaults will be set. If the battery's charge is marginal, it is possible for bogu

Page 5 - The FSUser check byte

The remaining bytes, 50 to 63, are not cleared by the FileStore as they are not used. The FSUser check byte The FSUser check byte is calculated by

Page 6 - NVRAM read code

There is a caveat to be aware of. I do not currently know if the FSUser command clears existing data or if it simply writes new data. For example, if

Page 7

FOR rec%=0 TO 5 : buffer%?rec%=0 : NEXT ?buffer%=addr% PROCcmosassemble(5) SYS "Econet_DoImmediate", 2, &E800, fsstn%, fsnet%, c

Page 8 - The 146818

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Acorn FileStore E01 User Manual

Browse online or download User Manual for Networking Acorn FileStore E01. FileStore RTC/NVRAM

Summary of Contents

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