Performance Motion Devices PR8358120, Руководство пользователя

Страница: 63 / 103

Accessing Card Resources
Prodigy/CME PC/104 User’s Guide
63
3
3.3 Accessing On-Card Resources
The most common use of the Prodigy/CME PC/104 card is to process commands to resources located on the card
itself. Typically this means communicating with the on-card Magellan Motion Processor, but it can also mean
communicating with other Prodigy/CME PC/104 on-card resources such as the dual-ported RAM. Figure 3-4 shows
this configuration.
Figure 3-4:
Host Controller
& On-card
Resources
Accessing on-card resources is straightforward using the PRP system. The on-card resource and the address are looked
up using the table
in Section 3.1.2, “PRP Resources,” on page 59 and then a PRP message corresponding to the desired
action is sent using those on-card resource and address values. The following example illustrates:
Example 1: A Host Controller wants to set the position of Axis 3 of the Prodigy/CME PC/104’s on-card Magellan
Motion Processor to a value of 0x123456.
From the table in Section 3.1.2, “PRP Resources,” on page 59 to communicate with the on-card Magellan Motion
Processor, a PRP message is sent to Resource ID 2 (corresponding to the MotionProcessor resource), to address 0
(corresponding to the Prodigy/CME PC/104’s on-card Magellan), with an action ID of 2 (corresponding to the
Command action). The message body is loaded with the Magellan packet corresponding to “Set Position, #3
0x123456,” which is the 3-word sequence 0x210, 0x0012, 0x3456.
Upon processing of this command, the host would receive a PRP message back. A zero in the status field would indi-
cate that no error occurred. If this is the case the message body will be empty. If an error did occur, then the PRP sta-
tus field would contain a 1, and the message body would contain the specific error code that occurred.
Example 2: The Host Controller reads the 32-bit word value of address 0x100 from the Prodigy/CME PC/104’s dual-
ported RAM
Here is the command that would be sent:
Upon successfully processing this command, the host would receive the 32-bit contents of memory location 0x100 in
the message body.
PRP MotionProcessor, Addr 0, Command // Send a command to the on-card Magellan Motion Processor. Message
// body contains Magellan Command “SetPosition #3, 0x123456”
PRP Memory, Addr 0, Read // Send a ‘Read’ action (ID: 7) to the PRP Memory Resource (ID: 3),
// address 0 (the address of the Prodigy/CME PC/104 on-card dual-
// ported RAM). The PRP message body contains a sub-action of 0,
// specifying a 32 bit word read, followed by 0x100 the address of the
// 32 bit word to read from the dual-ported RAM.
Ethernet/TCP
C-Motion
Engine
Magellan
Prodigy/CME
PC/104 Card
Host Controller