DS2196 datasheet(104/157 Pages) DALLAS

104 / 157 page

DS2196

104 of 157

Receive a 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 through 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 RHIR 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.

Transmit a HDLC Message

1. Make sure HDLC controller is done sending any previous messages and is current sending flags by

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

2. Enable either the THALF or TNF interrupt

3. Read THIR 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.

Transmit a BOC

1. Write 6–bit code into TBOC

2. Set SBOC bit in TBOC=1

DS2196 Datasheet(PDF) 104 Page - Dallas Semiconductor