Cirrus Logic AN118 - Manual (Page 8)

AN118
8 AN118REV2
board, and is entered by setting the DIPs to ‘111’.
Immediately upon entering mode 7, the
toggle_all_leds routine is called to blink the LEDs
repeatedly until the board is reset.
4. MAXIMUM SCLK RATE
A machine cycle in the 80C51 consists 12 oscillator
periods or 1
µ
s if the microcontroller’s oscillator
frequency is 12 MHz. Since the
CS5521/22/23/24/28’s maximum SCLK rate is
2MHz, additional no operation (NOP) delays may
be necessary to reduce the transfer rate if the micro-
controller system requires higher rate oscillators.
5. DEVELOPMENT TOOL
DESCRIPTION
The code in this application note was developed us-
ing a software development package from Franklin
Software, Inc. The code consists of intermixed C
and assembler algorithms which are used by the
CDB5521/22/23/24/28, a customer evaluation
board designed to help customers evaluate the per-
formance of the CS5521/22/23/24/28 devices.
6. CONCLUSION
This application note describes code that can be
used to interface an 80C51 to both the
CS5521/22/23/24/28 ADC and a PC. It is divided
into two main sections: hardware and software. The
hardware interface illustrates both a three-wire and
a four-wire interface between the 80C51 and the
ADC. The three-wire is SPI™ and MICROWIRE™
compatible. The software, developed with develop-
ment tools from Franklin Software, Inc., is used in
conjunction with the PC evaluation software and
the CDB5521/22/23/24/28 evaluation board to pro-
vide a system by which the CS5521/22/23/24/28’s
performance can be evaluated. There are four main
routines which interface the CS5521/22/23/24/28
to the 80C51, and provide the communication be-
tween the 80C51 and the PC, e.g. transfer_byte,
receive_byte, txser, and rxser. These four routines
are written in 80C51 assembly language, and are
easily imported into application-specific designs
by both C and assembly programmers.
All of the software described in this note is includ-
ed Section 7. “Appendix: 80C51 Microcontroller
Code” on page 9.