FX929B Datasheet, PDF (31/48 Pages) CML Microcircuits – Flexible Operating Modes

4-Level FSK Modem Data Pump
FX929B
1.6 Application Notes
1.6.1 Transmit Frame Examples
The operations needed to transmit a single Frame consisting of Symbol and Frame Sync sequences, Station
ID block, and one each Header, Intermediate and Last blocks are shown below:
1.
Ensure that the Control Register has been loaded with a suitable CKDIV value, that the IRQNEN
and TXRXN bits of the Mode Register are '1', the RXEYE, PSAVE and SSIEN bits are '0' and the
INVSYM bit is set appropriately.
2.
Read the Status Register to ensure that the BFREE bit is '1', then write 6 Symbol Sync bytes to the
Data Block Buffer and a T24S task to the Command Register.
3.
Wait for an interrupt from the modem, read the Status Register; the IRQ and BFREE bits should be
'1' and the IBEMPTY bit should be '0'.
4.
Write 6 Frame Sync bytes to the Data Block Buffer and a T24S task to the Command Register.
5.
Wait for an interrupt from the modem, read the Status Register; the IRQ and BFREE bits should be
'1' and the IBEMPTY bit should be '0'.
6.
Write 3 Station ID bytes to the Data Block Buffer and a TSID task to the Command Register.
7.
Wait for an interrupt from the modem, read the Status Register; the IRQ and BFREE bits should be
'1' and the IBEMPTY bit should be '0'.
8.
Write 10 Header Block bytes to the Data Block Buffer and a THB task to the Command Register.
9.
Wait for an interrupt from the modem, read the Status Register; the IRQ and BFREE bits should be
'1' and the IBEMPTY bit should be '0'.
10. Write 12 Intermediate Block bytes to the Data Block Buffer and a TIB task to the Command
Register.
11. Wait for an interrupt from the modem, read the Status Register; the IRQ and BFREE bits should be
'1' and the IBEMPTY bit should be '0'.
12. Write 8 Last Block bytes to the Data Block Buffer and a TLB task to the Command Register.
13. Wait for an interrupt from the modem, read the Status Register; the IRQ and BFREE bits should be
'1' and the IBEMPTY bit should be '0'.
14. Wait for another interrupt from the modem, read the Status Register; the IRQ, BFREE and
IBEMPTY bits should be '1'.
Note: The final symbol of the frame will start to appear approximately 2 symbol times after the Status Register
IBEMPTY bit goes to '1'; a further 16 symbol times should be allowed for the symbol to pass completely
through the RRC filter.
Note: The SSYM bits of the Mode Register may be altered at any time to change the transmitted 'S' symbols.
If a timing reference is required, then setting the Mode Register SSIEN bit to '1' will cause a µC interrupt after
every 'S' symbol transmitted - in which case the µC will have to distinguish between interrupts caused by the
BFREE bit going to '1', and those caused by the SRDY bit being set to '1'.
© 1997 Consumer Microcircuits Limited
31
D/929B/1