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SCI to SPI Peripheral Communication in V850ES Microcontrollers

CSI unit can be configured easily for one interface type or another, for this example, we connected the

two devices to the same pins, and switched from a type 3 interface (when reading the MAX6627) to a

type 4 interface (when reading the DS1722).

Two general-purpose I/O port pins are used to drive the MAX6627 Chip Select (/CS) and DS1722 Chip

Enable (CE) signals. Note that the /CS signal for the MAX6627 is active low, while the CE signal for the

DS1722 is active high.

Specifications

• 5 MHz crystal: 20 MHz system clock

• CSI00: communication with temperature sensors

• CSI00: 8-bit transmit and receive transfers, most significant bit (MSB) first

• CSI00 clock: fxx/4, 5 MHz (max. for MAX6627 and DS1722)

• Temperature data: signed 16-bit read data

• Temperature data from the MAX6627: nearest 1/16

of a degree

• DS1722: 10-bit accuracy (to the nearest 1/4

of a degree)

• Temperature display: decimal data, scrolling through the LED digits

• Timer TM00: periodic 1 millisecond (ms) interrupt for debouncing switches

2.6 Software Flowcharts

The demonstration program consists of the following major sections:

• Initialization code for the program, called before the main() program starts, including clock and

peripheral initialization

• The main program loop, which responds to switches by reading and reporting temperature

• Subroutines for temperature reading and display

• Subroutines for CSI00 peripheral access

• ing data in LED

The flowcharts here will describe initialization, the main program, temperature routines, and CSI

ftware

2.6.1 Program Startup and Initialization

For V850ES programs written in C language, the startup code for the C program is supplied by an

Subroutines for reading switches and display

peripheral access. Flowcharts are not included for timer access, switch reading, or the LED. The so

listings include this code.

assembly language startup file, generally named crte.s. This startup code specifies the reset vector,

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