Radiometrix Ltd, FRPC2

page 7

The sequence for a byte transfer from the Host to the FRPC2 (i.e. TX download) is asynchronous and

proceeds as follows:

1. HOST asserts TX Request line low to initiate transfer

2. Wait for FRPC2 to pull TX Accept low (i.e. request is accepted)

3. Set data lines to output and place LS nibble on the data lines

4. Negate TX Request (set to 1) to tell FRPC2 that data is present.

5. Wait for FRPC2 to negate TX Accept (i.e. data has been accepted)

Repeat steps 1-5 with MS nibble.

Notes:

• The data bus must not be set to output until step 3. i.e. after the FRPC2 has accepted the request.

The bus may be left as an output until the entire packet has been transferred to the FRPC2, it

should then be set back to input (default state).

• The FRPC2's normal response time to the initial TX Request may be up to 1ms, thereafter, for the

duration of the packet, the response will be fast.

• The FRPC2 will ignore a TX Request from the Host while it is receiving a packet from the radio. If

the incoming packet fails it's error check the FRPC2 will respond to the TX Request as normal, i.e.

the TX Accept from the FRPC2 will be delayed until the incoming packet has finished. If a valid

packet is received this must be uploaded to the Host before the FRPC2 can respond to the Host’s TX

Request. Thus an RX Request will be signalled to the Host and not the expected TX Accept and the

Host must upload the incoming packet before the TX packet can be downloaded. The TX Request

should be left asserted (low) during the upload. The FRPC2 will respond as normal after the upload

is completed.

• For the above reason it is often easier to use RX Request to trigger a HOST interrupt and upload the

FRPC2 to the HOST under interrupt control.

• See Appendix B and C. for example FRPC2 driver subroutines.

figure 7: TX download timing diagram