RF430CL331HIPWR datasheet(29/60 Pages) TI1

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Block Requested

1. PCD ± Read Binary Request

Filling Block

2. Host ± Service Request

Being Transmitted

3. PCD/Host ± Data Being Transmitted (prefetch interrupt):

Filling Now

Sent

4. PCD/Host ± Next Request (only prefetch interrupt):

Being Transmitted

Have

Need

Buffer shifted internally:

Request Parameters:

buffer_start_index = L

length_requested = N - L

Entire Buffer Space (not to scale)

Filling Now

Sent

5. PCD/Host ± Next Request (only prefetch interrupt):

Sent

Being Transmitted

Filling

6. PCD ± Next Request (General Type 4 Request interrupt)

8. Next: Cycle repeats (to Step 3)

(up to limit)

7. Host ± Service Request:

Sending

N (<255 bytes)

RF430CL331H

www.ti.com

SLASE18A – SEPTEMBER 2015 – REVISED NOVEMBER 2015

5.9.3.1

NDEF Read Command With Prefetch Internal Buffer Handling

Figure 5-12. Read Buffer Flow (Prefetch Feature)

The key feature with Prefetch is that while the Read Binary is being transmitted, the next packet can be

sent out by the host controller and be filling the internal RF430CL331H buffer. Each request is stored in

the subsequent buffer memory until the buffer limit is reached. When the buffer limit is reached, the

remaining unsent data is shifted to the beginning of the buffer and what data is needed for the next

request is requested (see Step 6). This command is requested using the General Type 4 request interrupt

(not with a prefetch interrupt) because it does not happen during the time when the RF430CL331H is

sending data over RF.

Read buffer flow procedure (see Figure 5-12):

1. PCD requests a block of data.

2. PICC received the requests, sets up the internal register and asserts the INTO interrupt.

3. Host services the interrupt by supplying the data. PICC transmits the data. After starting to transmit the

data, PICC issues a Read Prefetch interrupt. The host supplies the extra data while the RF

communication is ongoing.

4. When the next Read Binary request comes, because the data is already cached, only the Prefetch

interrupt is asserted.

5. This time a Prefetch interrupt is asserted, but only a portion of the data can be written because the

buffer space is running out.

6. Because there is not enough data to service the Read Binary requests, a General Type 4 interrupt is

asserted. The partial data that has been written previously is shifted to the beginning of the buffer and

the only the remaining missing data is requested in the interrupt.

7. The complete data is sent out. The cycle repeats (the Prefetch interrupt is issued again).

If a prefetch interrupt is issued for a file, but there is no more data to send, this interrupt can be canceled

by servicing it by setting the data length sent to 0. Also if data was sent by a prefetch but it was not

needed by the RF430CL331H (due to a different request by the PCD) that data is discarded and the new

request handling initiated.

Detailed Description

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