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snap ethernet-based i/o units protocols and programming guide

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Starting Address Length Type Description<br />

FFFF F0D4 00D0 30 -- Pad for alignment<br />

Last valid address for this area: FFFF F0D4 FFFF<br />

Scratch Pad—Read/Write<br />

(Other timers follow in order on even 80 hex boundaries.)<br />

(Does not apply to SNAP Simple I/O) For SNAP Ethernet brains, only Scratch Pad bits apply. For<br />

SNAP Ultimate brains, all addresses apply <strong>and</strong> the Scratch Pad area is used to share data among<br />

devices on the network. Since each Scratch Pad read or write operation is atomic, reads <strong>and</strong><br />

writes will not interfere with each other.<br />

For more information on using the Scratch Pad area, see page 26.<br />

NOTE: Scratch Pad strings can be null terminated or can be binary strings with embedded nulls.<br />

Length is automatically calculated, but can be written to force a specific length. If the length <strong>and</strong><br />

the string are written together, the length written is used.<br />

Starting Address Length Type Description<br />

FFFF F0D8 0000 8 M Current state of Scratch Pad bits (mask).<br />

1 = bit on; 0 = bit off.<br />

FFFF F0D8 0400 8 M Set Scratch Pad On mask. 1 = set bit on; 0 = no change.<br />

FFFF F0D8 0408 8 M Set Scratch Pad Off mask 1 = set bit off; 0 = no change.<br />

FFFF F0D8 1000 4 I Scratch Pad integer element 0.<br />

FFFF F0D8 1004 4 I Scratch Pad integer element 1.<br />

FFFF F0D8 1008 4 I Scratch Pad integer element 2.<br />

(Additional integer elements follow in order on even 4 hex boundaries.<br />

Total at this address: 1024. Additional 2048 starting at address FFFF F0DA 0000)<br />

FFFF F0D8 1FFC 4 I Scratch Pad integer element 1023.<br />

FFFF F0D8 2000 4 F Scratch Pad float element 0.<br />

FFFF F0D8 2004 4 F Scratch Pad float element 1.<br />

FFFF F0D8 2008 4 F Scratch Pad float element 2.<br />

(Additional float elements follow in order on even 4 hex boundaries.<br />

Total at this address: 1024. Additional 2048 starting at address FFFF F0DC 0000)<br />

FFFF F0D8 2FFC 4 F Scratch Pad float element 1023.<br />

FFFF F0D8 3000 2 UI Scratch Pad string element 0: Length (integer). If length is not<br />

written here, it is automatically calculated by counting to the first null.<br />

FFFF F0D8 3002 80 S-PL Scratch Pad string element 0: String<br />

SNAP Ethernet-Based I/O Units Protocols <strong>and</strong> Programming Guide 129

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