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Sensoray Model 621/721 Instruction Manual

Page 7

A relay channel must be "armed" before it will capture a detected edge.

An internal ARM Capture register is used to arm or disarm edge capturing. A “1” in the corresponding

channel position will allow edge capturing while a “0” will disable edge capturing on that channel.

The host system does not have direct access to this register. It is written to using the ARM Control register and

the “ARM” bit of the “Data direction/Misc./Status” register.

If ARM bit = “1”: All channels whose corresponding bit in the ARM Control register is a “1” are

armed. Those channels with a “0” in the ARM Control register remain unchanged.

If ARM bit = “0”: All channels whose corresponding bit in the ARM Control register is a “1” are

disarmed. Those channels with a “0” in the ARM Control register remain

unchanged.

See Figure 2 for a diagram of the process.

Reading the “ARM Control” register accesses the internal ARM Capture register directly and will give

the current status of the register. A “0” means that channel is disabled while a “1” shows it is armed.

If a channel is armed for edge capture and the same channel is set for output, a change in output level

could result in a captured event. Unless you want a “loop-back” event, a channel set for output should

have capturing disabled.

5.2.6 Edge Capture Flag Register (channels 0-63)

Each channel is associated with a one-bit capture register. The capture register is responsible for logging

the occurrence of a detected edge. When a selected edge occurs while capture is enabled, the associated

capture flag is set. All of the capture flags can be read through the edge capture flag port.

Note: before the capture register can log a detected edge, the channels capture register must be armed.

After capturing an edge, the capture register remains set until explicitly reset (cleared) by the host.

5.2.7 Clearing Captured Edges

Sometime after a captured edge is detected, it is necessary to reset the associated capture register. This is

accomplished by disarming the associated “arm capture” register.

Set Reset Set Reset

Bit 0Bit 1

ResetSet

Bit 30Bit 31

Reset Set

Internal ARM Capture Register

Bit 31 Bit 30 Bit 0Bit 1

Internal ARM Control Register

Bit 14Bit 15

Data Direction/Misc./Status Register

Bit 13

ARM XX Channel 31 Channel 30 Channel 1 Channel 0

Figure 2

1 2 3 4 5 6 7 8 9 10 11 12 13

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