User manual

Consumer-band BPSK 7.2 kbps PLM PICtail™ Plus Daughter Board User’s Guide

The memory and MIPS requirements for the modem software for different baud rates

(with DMA and RAM-saving options enabled) are listed in Table 3-1

TABLE 3-1: MEMORY AND MIPS REQUIREMENTS FOR THE MODEM

3.1.6 Developing Custom Applications

An application template has been provided to ease the development of customized

PLM applications. The application template can be downloaded from the

Consumer-band BPSK 7.2 kbps PLM PICtail Plus Daughter Board web site at:

www.microchip.com/powerline.

By default, the software for the daughter board is designed to operate on a carrier

frequency of 129.6 kHz. However, if required, the software can be modified to operate

at a different carrier frequency. In this case, the following need to be taken into

consideration:

• The hardware provided in the kit is designed to operate at a carrier frequency of

129.6 kHz. Changing the carrier frequency in software will require modifications to

the hardware components, specifically the components that decide the filter cutoff

frequencies

• It is necessary for the carrier frequency to be an integral multiple of the baud rate:

Carrier frequency, F

= k * baud, k

Integer

• Lower carrier frequencies result in lower maximum possible data rates

• Carrier frequency or baud rate changes outside the combinations provided in the

include file (

...\modem\bpsk\bpsk_filter.inc) will require recalculation of

digital filter coefficients

• Increasing carrier frequency increases the MIPS requirement for the modem soft-

ware. For this reason, the carrier frequency must be well within the CPU’s useful

performance limit. The modem software requires approximately 0.234 to 0.303

MIPS/kHz of carrier frequency

Baud Rate RAM (Bytes) Flash (Bytes) MIPS

1200 700 2709 33.5

2400 412 2709 33.6

3600 316 2709 33.7

4800 268 2709 33.9

5400 252 2709 33.9

7200 220 2709 34.1