M32CSLASH86 datasheet(216/505 Pages) RENESAS

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17. Serial I/O (Clock Synchronous Serial I/O)

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17.1 Clock Synchronous Serial I/O Mode

In clock synchronous serial I/O mode, data is transmitted and received with the transfer clock. Table 17.1

lists specifications of clock synchronous serial I/O mode. Table 17.2 lists register settings. Tables 17.3 to

17.5 list pin settings. When UARTi (i=0 to 4) operating mode is selected, the TxDi pin outputs a high-level

("H") signal before transfer starts (the TxDi pin is in a high-impedance state when the N-channel open drain

output is selected). Figure 17.10 shows transmit and receive timings in clock synchronous serial I/O mode.

Table 17.1 Clock Synchronous Serial I/O Mode 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=f1, f8, f2n(1) m :setting value of the UiBRG register, 0016 to FF16

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

Transmit/Receive Control

_______

_______ _______

Selected from the CTS function, RTS function or CTS/RTS function disabled

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)

________

_______

- Apply a low-level ("L") signal to the CTSi pin when the CTS function is selected

Receive Start Condition

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

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

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

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

Interrupt Request Generation Timing • While transmitting, the following conditions can be selected:

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

when data is transferred from the UiTB register to the UARTi transmit register (transfer started)

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

when a data transfer from the UARTi transmit register is completed

• While receiving

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

Error Detect

Overrun error(3)

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

the UiRB register

Selectable Function

• CLK polarity

Transferred data output and input are provided on either the rising edge or falling edge

of the transfer clock

• LSB first or MSB first

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

• Continuous receive mode

Data can be received simultaneously by reading the UiRB register

• Serial data logic inverse

This function inverses transmitted/received data logically

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 "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 "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).

2(m+1)

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