M16C80 Datasheet, PDF (322/358 Pages) Renesas Technology Corp – RENESAS 16-BIT SINGLE-CHIP MICROCOMPUTER M16C FAMILY / M16C/80 SERIES

M16C/80 Group
32. Standard serial I/O mode
32.2 Overview of standard serial I/O mode 2 (clock asynchronized)
In standard serial I/O mode 2, software commands, addresses and data are input and output between the
MCU and peripheral units (serial programer, etc.) using 2-wire clock-asynchronized serial I/O (UART1).
Standard serial I/O mode 2 is engaged by releasing the reset with the P65 (CLK1) pin "L" level.
The TxD1 pin is for CMOS output. Data transfer is in 8-bit units with LSB first, 1 stop bit and parity OFF.
After the reset is released, connections can be established at 9,600 bps when initial communications (Fig-
ure 32.20) are made with a peripheral unit. However, this requires a main clock with a minimum 2 MHz input
oscillation frequency. Baud rate can also be changed from 9,600 bps to 19,200, 38,400, 57,600 or 115,200
bps by executing software commands. However, communication errors may occur because of the oscilla-
tion frequency of the main clock. If errors occur, change the main clock's oscillation frequency and the baud
rate.
After executing commands from a peripheral unit that requires time to erase and write data, as with erase
and program commands, allow a sufficient time interval or execute the read status command and check
how processing ended, before executing the next command.
Data and status registers in memory can be read after transmitting software commands. Status, such as
the operating state of the flash memory or whether a program or erase operation ended successfully or not,
can be checked by reading the status register. Here following are explained initial communications with
peripheral units, how frequency is identified and software commands.
Initial communications with peripheral units
After the reset is released, the bit rate generator is adjusted to 9,600 bps to match the oscillation fre-
quency of the main clock, by sending the code as prescribed by the protocol for initial communications
with peripheral units (Figure 32.20).
(1) Transmit "0016" from a peripheral unit 16 times. (The MCU with internal flash memory sets the bit
rate generator so that "0016" can be successfully received.)
(2) The MCU with internal flash memory outputs the "B016" check code and initial communications end
successfully *¹. Initial communications must be transmitted at a speed of 9,600 bps and a transfer
interval of a minimum 15 ms. Also, the baud rate at the end of initial communications is 9,600 bps.
*1. If the peripheral unit cannot receive "B016" successfully, change the oscillation frequency of the main
clock.
Peripheral unit
MCU with internal
flash memory
Reset
(1) Transfer "0016" 16 times
1st
At least 15ms
transfer interval
2nd
"0016"
"0016"
15 th
16th
"0016"
"0016"
"B016"
(2) Transfer check code "B016"
The bit rate generator setting completes (9600bps)
Figure 32.20 Peripheral unit and initial communication
Rev.1.00 Aug. 02, 2005 ^{Page 311} of 329
REJ09B0187-0100