SPRUJ79 November 2024 F29H850TU , F29H859TU-Q1
The parallel general-purpose I/O (GPIO) boot mode asynchronously transfers code from the host to C29x internal memory. Each value is 8-bits long and follows the same data flow as outlined in Figure 4-9.
The control subsystem communicates with the external host device by polling/driving the Host Control and C29x control lines. The handshake protocol shown in Figure 4-10 must be used to successfully transfer each word using GPIO [D0:D7]. This protocol is very robust and allows for a slower or faster host to communicate with the controller subsystem.
Two consecutive 8-bit words are read to form a single 16-bit word. The least-significant byte (LSB) is read first followed by the most-significant byte (MSB). In this case, data is read from GPIO[D0:D7].
The device first signals the host that the device is ready to begin data transfer by pulling the C29x control pin low. The host load then initiates the data transfer by pulling the DSP control pin low. The complete handshake protocol is shown in Figure 4-10.
This process is repeated for each data value to be sent.
Figure 4-11 shows the transfer flow from the host side. The operating speed of the CPU and host are not critical in this mode as the host waits for the device and the device in turn waits for the host. In this manner, the protocol works with both a host running faster and a host running slower than the device.