J058 SCRAM

Section 5. Using the SCRAM

Installing memory chips

When installing memory devices, please observe the following points:

  1. 2K devices only have 24 pins. Locate them in the 28-pin sockets thus:

    Figure 11. Memory Device Location

    8K device (28 pins) pin 1 →    U   
         
    2K device (24 pins) pin 1 →   U  
         
       
       
       
       
       
       
       
       
       
       
  2. Make sure that none of the pins are bent, and that the chips are properly pushed down.

  3. Ensure that you have changed the relevant links (links 4, 5, 7, 8-13)

Re-adjusting timekeeping

If re-adjusting the frequency of the RTC clock oscillator, attach your probe to the CKOUT pin (pin 21) of IC15 to avoid loading the oscillator circuit. Adjust the trimmer TC1 for a clock frequency of 32.768 kHz.

Care of the board

CAUTION:

When removing the board, take care to place it where there is no risk of any metallic or liquid conductors shorting out the tracks on the bottom side of the board, since this not only risks corrupting the data held on the board, but may also damage the battery through excessive current drain. Anti-static bench surfaces may also shorten the data retention time.

In the following examples, standard Arcom BASIC programming language is used. The board links are assumed to be as standard, i.e. with the RTC at I/O addresses 80-8F (128-143 decimal, only two bytes of its internal RAM available), and the RAM in memory locations 32768-45055 (six 2K devices present). Make sure that links 8-13 cause power to be taken from the battery so that the dataand time are retained on power-down (connect the B side).

RTC Examples

PROGRAM 1

10 REM A program to load the RTC with the time & date.
20 OUT 138,32
30 OUT 139,6
35 REM (The above 2 lines set the clock running normally)
40 PRINT"Please enter the time in the following format:"
50 PRINT"Hours,Minutes,Seconds,Date,Month,Year."
55 PRINT"E.g: 5,45,0,13,10,84"
60 INPUT HR,HN,SC,DT,MT,YR
70 OUT 132,HR
80 OUT 130,MN
90 OUT 128,SC
100 OUT 135,DT
110 OUT 136,MT
120 OUT 137,YR
130 PRINT"Now switch off the power then load program 2."
140 END

PROGRAM 2

10 REM A program to check that the RTC has kept correct
20 REM time during power-down.
30 PRINT"The time is ";INP(132);":";INP(130);":";INP(128)
40 PRINT"The date is ";INP(135);":";INP(136);":";INP(137)
50 END