DS2152 datasheet(59/97 Pages) MAXIM

59 / 97 page

DS2152

59 of 97

12.1.3 Receive an HDLC Message or a BOC

1) Enable RBOC and RPS interrupts.

2) Wait for interrupt to occur.

3) If RBOC = 1, then follow steps 5 and 6.

4) If RPS = 1, then follow steps 7 thru 12.

5) If LBD = 1, a BOC is present, then read the code from the RBOC register and take action as needed.

6) If BD = 0, a BOC has ceased, take action as needed and then return to step 1.

7) Disable RPS interrupt and enable either RPE, RNE, or RHALF interrupt.

8) Read RPRM to obtain REMPTY status.

a. If REMPTY = 0, then record OBYTE, CBYTE, and POK bits and then read the FIFO .

a1. If CBYTE = 0 then skip to step 9.

a2. If CBYTE = 1 then skip to step 11.

b. If REMPTY = 1, then skip to step 10.

9) Repeat step 8.

10) Wait for interrupt, skip to step 8.

11) If POK = 0, then discard whole packet, if POK = 1, accept the packet.

12) Disable RPE, RNE, or RHALF interrupt, enable RPS interrupt and return to step 1.

12.1.4 Transmit an HDLC Message

1) Make sure HDLC controller is finished sending any previous messages and is currently sending flags

by checking that the FIFO is empty by reading the TEMPTY status bit in the TPRM register.

2) Enable either the THALF or TNF interrupt.

3) Read TPRM to obtain TFULL status.

a. If TFULL = 0, then write a byte into the FIFO and skip to next step (special case occurs when the

last byte is to be written, in this case set TEOM = 1 before writing the byte and then skip to step

6).

b. If TFULL = 1, then skip to step 5.

4) Repeat step 3.

5) Wait for interrupt, skip to step 3.

6) Disable THALF or TNF interrupt and enable TMEND interrupt.

7) Wait for an interrupt, then read TUDR status bit to make sure packet was transmitted correctly.

12.1.5 Transmit a BOC

1) Write 6-bit code into TBOC.

2) Set SBOC bit in TBOC = 1.

DS2152 Datasheet(PDF) 59 Page - Maxim Integrated Products