Commodore 2001-8 User Manual page 86

BUSIDEVICE CONTROL
The line-pin connections for the 12 position, 24 contact edge card Connector, emanate from the PET main
assembly board (see Table 7-19). For further information. please refer to Figure 7.2
Certain physical limitations should be noted when connecting devices to the IEEE bus:
a) The maximum advisable bus extension from the PET is 20 meters.
b) The maximum interdevice spacing is 5 meters.
c) The maximum number of devices is 15.
PET
PET
Contact
a",
IEEE
Contact Label
Identifi- Label Identifi-
Deseription
cation cation
1
DATA 0101
1
Data INPUT/OUTPUT lINE-#"l
2 0102 2
Data INPUT/OUTPUT LINE #2
3 0103 3 Data INPUT/OUTPUT LINE #3
4 0104 4
Data INPUT/OUTPUT LINE #4
5
MANAGER
EOI
5
End Or identify
6 TRANSFER DAV
6
Data valid
7
NRFD
7
Not ready. tor data
8
NDAC 8
Data not accepted
9 MANAGER IFC
9
Interlace clear
Same as PET reset
10 SRO 10 Service request
11 ATN 11
Attention
12
SHIELD 12
Chassis ground and IEEE
cable shield
A DATA 0105
13 Data INPUT/OUTPUT LINE #5
B
0106 14 Data INPUT/OUTPUT L1NE.tffi
C
0107 15 Data INPUT/OUTPUT LINE #7
D 0108
16 Data INPUT/OUTPUT L1NE.;t8
E MANAGER REN 17
Remote enable \REN) always
ground in the PET
F GROUNDS
GNOG 18 OAV ground
H GN07 19 NFRO ground
J GN08 20 NOAC ground
K GN09 21
IFC ground
L
GN010 22 SRO ground
M GN011
23 A ~N ground
N LOGIC GNO 24 Data ground (0101-81
Table 7.20. IEEE bus group, label and contact Identification number.
THE DATA BUS
This bus is comprised of 8 bi-directional lines that transmit the active low data signals D101-8. The
slowest device in use on the bus at a given time controls the rate of data transfer; the mode of transfer is
one byte at a time, bit parallel.
Peripheral addresses and control information are also transmitted on the data bus. They are
differentiated from data by ATN (true) during their transfer.
The most significant bit (MSS) is on line D 108.
For an explanation of signal abbreviations such as D 1-08, see Figure 7.23.
Data Transmission Modes
All possible bit patterns are valid on the data bus when sending data to devices.
THE TRANSFER BUS
This three line bus controls the transfer of data over the data bus. The signals transmitted are used in
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