M32C83T datasheet(227/527 Pages) RENESAS

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16. Serial I/O (Special Function)

)

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16.4 Special Mode 2

In special mode 2, serial communication between one or multiple masters and multiple slaves is available.

_____

The SSi input pin (i=0 to 4) controls the serial bus communication. Table 16.19 lists specifications of special

mode 2. Table 16.20 lists registers to be used and settings. Tables 16.20 to 16.22 list pin settings.

Table 16.19. Special Mode 2 Specifications

Item

Specification

Transfer Data Format

Transfer data : 8 bits long

Transfer Clock

The CKDIR bit in the UiMR register (i=0 to 4) is set to "0" (internal clock selected) : fj/2(m+1)

fj = f1, f8, f2n(1) m : setting value of the UiBRG register

0016 to FF16

The CKDIR bit to "1" (external clock selected) : input clock from the CLKi pin

Transmit/Receive Control

______

SSi input pin function

Transmit Start Condition

•To start transmitting, the following requirements must be met(2) :

- Set the TE bit in the UiC1 register to "1" (transmit enable)

- Set the TI bit in the UiC1 register to "0" (data in the UiTB register)

Receive Start Condition

• To start receiving, the following requirement must be met(2) :

- Set the RE bit in the UiC1 register to "1" (receive enable)

- Set the TE bit to "1" (receive enable)

- Set the TI bit to "0" (data in the UiTB register)

Interrupt Request

• Transmit interrupt timing can be selected from the followings:

Generation Timing

- The UiIRS bit in the UiC1 register is set to "0" (no data in a transmit buffer) :

when data is transferred from the UiTB register to the UARTi transmit register (transmission

started)

- The UiIRS register is set to "1" (transmission completed):

when data transmission from UARTi transfer register is completed

• Receive interrupt timing

When data is transferred from the UARTi receive register to the UiRB register (reception completed)

Error Detection

•Overrun error(3)

This error occurs when the seventh bit of the next received data is read before reading the

UiRB register

•Fault error

______

In master mode, the fault error occurs an "L" signal is applied to the SSi pin

Selectable Function

• CLK polarity

Select from the rising edge or falling edge of the transfer clock when transferred data is output and input

• LSB first / MSB first

Data is transmitted or received in either bit 0 or in bit 7

• Continuous receive mode

Reception is enabled simultaneously by reading the UiRB register

• Serial data logic inverse

This function inverses transmitted or received data logically

• TxD, RxD I/O polarity Inverse

TxD pin output and RxD pin input are inversed. All I/O data levels are also inversed

• Clock phase

Select from one of 4 combinations of transfer data polarity and phases

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• SSi input pin function

Output pin is placed in a high-impedance state to avoid data conflict between master and other

masters or slaves

NOTES:

1. The CNT3 to CNT0 bits in the TCSPR register select no division (n=0) or divide-by-2n (n=1 to 15).

2. To start transmission/reception when selecting the external clock, these conditions must be met after the CKPOL bit

in the UiC0 register is set to "0" (data is transmitted on the falling edge of the transfer clock and data is received on the

rising edge) and the CLKi pin is held high ("H"), or when the CKPOL bit is set to "1" (Data is transmitted on the rising

edge of the transfer clock and data is received on the falling edge) and the CLKi pin is held low ("L").

3. If an overrun error occurs, the UiRB register is indeterminate. The IR bit in the SiRIC register does not change to "1"

(interrupt requested).

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