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SCC.DOC
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1990-09-20
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7KB
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187 lines
SCC notes (very brief)
Part 1 ---- IMP
Part 2 ---- Construction
Part 3 ---- Telcom
Part 1 IMP
------------------------------------------------------------------------
| Note IMPORTANT |
| |
| for use on some boards such as the earlier 'ROS' boards use 'RX' |
| and 'TX' disabling 1k block request otherwise you will hang on a |
| transfer of more than 128 blocks |
| |
------------------------------------------------------------------------
I2B-SCC.ASM - MicroBee 128k computer with 8530 (SCC) hardware
installed as per MicroBee drawing 8432-4-01
test version started 25/02/87 by Tony Ellis VK2ZNH
interrupts from 8530, no autocall when used with BeeModem
having 300 1200/75 and 75/1200 baud options. Autocall with 'Hayes' types.
to implement the split rates pin 3 must be connected to pin 6 on Port A
DTR does not have an RS232 driver, so RTS is toggled at the same time and
can be used instead of DTR for that function ( it does have a driver )
high-speed options upto 57600 baud provided for direct bee-to-another
micro links.
imp244.obj patched - replaced 110 bps option with 75/1200 bps option
and 600 bps with 1200/75 option (consequently times shown for split baud
rate transfers are incorrect !!
operates in full duplex with split baud rates using port A
(that is the one nearest to the DIN power connector)
NB this is different to Telcom which uses Port B
Split rates
Selecting speed of 75 bps gives Tx = 1200 bps Rx = 75 bps
Selecting speed of 1200 bps gives Tx = 75 bps Rx = 1200 bps (normal use)
-----------------------------------------------------------------------------
SUGGESTED PIN CONNECTIONS FOR ADAPTOR CABLE for IMP (Port A)
15 pin male connector 25 pin female connector
+10.5 volts for BeeModem
pin 1 -------------------------------- pin 9
DTR/RTS
pin 2 -------------+------------------ pin 4
|
------------------- pin 20
pin 3 ------- TRxC
|
pin 6 ------- RTxC
TxD
pin 9 -------------------------------- pin 2
CTS
pin 11 ------------------------------- pin 5
RxD
pin 13 ------------------------------- pin 3
GND
pin 15 ------------------------------- pin 7
Part 2 Construction Notes
Parts list
G2 Crystal 3.6864 MHz source Geoff Wood in Lane Cove
X3 D15 right angle female type 15SCA Port B
X4 D15 right angle female type 15SCA Port A
IC42 Zilog 8530 SCC source George Brown on Paramatta Road
IC43 74LS04
IC44 74LS164
IC45 1489
IC46 74LS74
IC47 1488
IC48 74LS32
IC50 7660
Sockets to suit (Makes fault finding much easier - use good quality dual-wipe)
C44-51 .1 mfd chip monolithic
C53-55 .1 mfd chip monolithic
C56 10 mfd Tantalum
C57 10 mfd Tantalum
R8 4.7k resistor
D3 OA91 or similar
D4 IN914/IN4148 or similar
D5 IN914/IN4148 or similar
A Larger Heatsink for the two 5 volt Rectifiers is needed for reliability.
The one (or two on some early machines) are just not effective enough.
N.B. HARD-DISK owners. (only, and not applicable to all harddisk machines)
1. The W3 123 pads beside the SCC need changing to put the SCC second priority
in the Interrupt daisy chain. On the none-component side cut the link between
W3-2 and W3-3 and make a connection between W3-1 and W3-2. This ensures the
hard-disk is still the highest priority.
2. The 4Mhz oscillator is needed for the SCC clock. Therefore the following
parts must all be installed. Fit any that are missing.
IC40 74LS04
G1 4 MHz crystal
C39 .01 mfd
C40 220pf
R4,R5 1k resistor
Connection Details for Port A and Port B
pin 1 +10.5 volts
pin 2 RTS RS232 level
pin 3 TRxC TTL level
pin 4 DTR TTL level
pin 5 RTS TTL level
pin 6 RTxC
pin 7 NC
pin 8 DCD TTL level
pin 9 TxD RS232 level
pin 10 TxD TTL level
pin 11 CTS RS232 level
pin 12 -9 volts
pin 13 RxD RS232 level
pin 14 +5 volts
pin 15 GND
Note: there is an internal connection between pin 3 Port A and pin 3 Port B
on the PC board.
Some things to be aware of:-
1. Make sure your power supply is no more than 10.5 volts - otherwise the
7660 IC gets a bit upset...
2. If using a long ribbon cable on Port B, then cut the clock line close to
the 'Bee connector, or otherwise the oscillator may be unreliable.
3. Some Version 3 boards will not work without a capacitor on the write line
to supress a glitch. This can be fixed by adding a 47 to 220pf capacitor
be-tween pins 3 and 7 of IC33. This is NOT needed on Version 4 boards.
Part 3 Telcom Notes
To use BeeModem with Telcom 2.3 use Port B (i.e. one nearest disk cable)
Make a D15 male to D25 pin female adaptor cable as follows
15 pin connector 25 pin Connector
pin 1 pin 9 +10.5 volts
pin 9 pin 2 TxData
pin 11 pin 5 CTS
pin 13 pin 3 RxData
pin 15 pin 7 GND
Select port 2 on the Telcom Menu and off you go!
The information here is correct to the best of my knowledge. Please leave a
message describing any omissions or needed corrections which will go into the
next version. Leave me a note on SMUG bulletin board if you have problems ...
(02) 476 6396 ... or the MicroBee Conference ...
In information from AAPRA (the Packet Radio people) is seems that there
is a track missing on some 128k core-boards that affects the SCC. The missing
track is from IC49 pin 4 or IC41 pin 1 (which are connected) to IC33 pins 2
and 4. Check your board, and if missing, fit it. It affects the chip reset and
on a few boards has stopped the SCC from working properly.
Tony Ellis VK2ZNH 15/07/89