Cypress Semiconductor FX2LP Informacje Techniczne Pobierz pdf (Strona 225)

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Chapter 10. General Programmable Interface (GPIF) Page 10-35

To perform a Single-Read transaction:

1. Initialize the GPIF Configuration Registers and Waveform Descriptors.

2. Perform a dummy read of the XGPIFSGLDATLX register to start a single transaction.

3. Wait for the GPIF to indicate that the transaction is complete. When the transaction is com-

plete, the DONE bit (GPIFIDLECS.7 or GPIFTRIG.7) will be set to 1. If enabled, a GPIFDONE

interrupt will also be generated.

4. Depending on the bus width and the desire to start another transaction, the read data can be

retrieved from the XGPIFSGLDATH, XGPIFSGLDATLX, and/or the

XGPIFSGLDATLNOX register (or from the SFR-space copies of these registers):

In 16-bit mode only, the most significant byte, FD[15:8], of data is read from the

XGPIFSGLDATH register.

In 8- and 16-bit modes, the least significant byte of data is read by either:

• reading XGPIFSGLDATLX, which reads the least significant byte and starts another Sin-

gle-Read transaction.

• reading XGPIFSGLDATLNOX, which reads the least significant byte but does not start

another Single-Read transaction.

The following C program fragments (Figures 10-17 and 10-18) illustrate how to perform a Sin-

gle-Read transaction in 8-bit mode (WORDWIDE=0):

1 2 ... 220 221 222 223 224 225 226 227 228 229 230 ... 459 460

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