Allen-Bradley 1747-OC Series, User Manual

Page: 21 / 126

1747-UM001A-US-P - March 2000
Introducing the Open Controller 1-9
OC_ReadSRAM
OC_WriteSRAM
These functions are not available in the DOS API.
Timer
Both open controllers include programmable timers capable of generating
interrupts. However, the hardware implementation and functionality of
these timers are very different. The timers are not supported by the open
controller APIs. More information is available upon request from Rockwell
Automation Technical Services.
The 1747-OCF has an auxiliary 8254 timer. All three of the 8254 timers
have access to a single PCI interrupt or NMI. A status register can be read to
determine which of the timers set the interrupt. The timers can also be
cascaded to form a 32- or 48-bit timer.
Dual port register (DPR) memory window jumper
The 1747-OCF has a jumper for selecting whether BIOS maps the 8K byte
DPR memory window above or below the 1 Mbyte memory address. The
1747-OCE only supports memory window addresses below 1 Mbyte, within
the OC_OpenScanner function call. See 1746 I/O Interface and 1747-OC
Open Controller API Software User Manual, publication
1747-UM002A-US-P, for more information.
To use the DOS API, set the jumper to map the memory window below 1
Mbyte. To use the NT API, set the jumper to the “32-bit” (above 1 Mbyte)
position. Refer to "Setting Jumpers" on page 2-3 for additional information.
Summary of API Differences
The NT (version 1.03) and DOS (version 1.04) APIs are compatible with
both open controllers. Most applications should work on both hardware
platforms without modification. Table 1.A lists platform-dependent API
functions.
Table 1.A
Platform-dependent API functions
API Function 1747-OCE 1747-OCF
OC_ReadRtcSRAM
supported not supported
OC_WriteRtcSRAM
supported not supported
OC_ReadSRAM
not supported supported (NT only)
OC_WriteSRAM
not supported supported (NT only)
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