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Analog Modules: The maximum number of analog input modules that can provide input data to the host is 8; however, there may be additional modules in the remote drop configured outside the Remote I/O Scanner's I/O map. The maximum number of analog input modules that can be configured for a remote drop is 29. Similarly, while the maximum number of analog output modules that can receive output data from the host is 16, as many as 54 can be configured for a remote drop.
Option Modules: A remote drop with seven or fewer racks can contain up to 18 GDS (Graphics Display Coprocessor), or ADS (Alphanumeric Display Coprocessor) modules, or up to 9 PCM (Programmable Coprocessor) modules with daughterboards. Each PCM/daughterboard combination counts as two option modules against the total of 18. The following table shows how many GDS and/or ADS modules can be used with 0 to 9 PCMs.
Total Option Modules in a Remote Drop
Number of PCMs and | Number of GDS and/ |
Daughterboards | or ADS Modules |
|
|
0 | 18 |
1 | 16 |
2 | 14 |
3 | 12 |
4 | 10 |
5 | 8 |
6 | 6 |
7 | 4 |
8 | 2 |
9 | 0 |
|
|
If there are 8 racks in the remote drop, one less PCM with daughterboard, or two less GDS or
ADS modules are permitted.
Analog Expanders: A remote drop can accommodate up to one analog input module with eight expander modules. However, the maximum number of expanders that can pass inputs to the CPU is three, due to the Remote I/O Scanner's 128±byte input data limit. If an analog module and three expanders were used, no additional input modules (either analog or discrete) could communicate with the host from the remote drop.
Modules Not Supported: A remote drop cannot have any I/O module interrupts, or bus controllers or other modules that depend on COMREQ instructions for their operations.
Third±party VME modules cannot be used in a remote drop.
10 | Series 90±70 Remote I/O Scanner User's Manual ± July 1992 |
