M16C62N Datasheet, PDF (118/213 Pages) Renesas Technology Corp – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

UART2 Special Mode Register
Mitsubishi microcomputers
M16C / 62N Group (80-pin)
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Figure 1.14.26 shows the functional block diagram for I²C mode. Setting “1” in the I²C mode select bit
(IICM) causes ports P70, P71, and P72 to work as data transmission-reception terminal SDA, clock input-
output terminal SCL, and port P72 respectively. A delay circuit is added to the SDA transmission output,
so the SDA output changes after SCL fully goes to “L”. The amount of delay can be selected in the range
of 2 cycles to 8 cycles of f1 using UART2 special mode register 3 (at address 037516). Delay circuit select
conditions are shown in Table 1.14.10.
Table 1.14.10. Delay circuit select conditions
Digital delay is
selected
No delay
Register value
IICM SDDS DL
Contents
001
1
1
to ^{Digital delay is added}
111
0
0
(000)
When IICM = “0”, no delay circuit is selected. When IICM = “0”,
however, always make sure SDDS = “0”.
An attempt to read Port P71 (SCL) results in getting the terminal’s level regardless of the content of the
port direction register. The initial value of SDA transmission output in this mode goes to the value set in
port P70. The interrupt factors of the bus collision detection interrupt, UART2 transmission interrupt, and
of UART2 reception interrupt turn to the start/stop condition detection interrupt, acknowledgment non-
detection interrupt, and acknowledgment detection interrupt respectively.
The start condition detection interrupt refers to the interrupt that occurs when the falling edge of the SDA
terminal (P70) is detected with the SCL terminal (P71) staying “H”. The stop condition detection interrupt
refers to the interrupt that occurs when the rising edge of the SDA terminal (P70) is detected with the SCL
terminal (P71) staying “H”. The bus busy flag (bit 2 of the UART2 special mode register) is set to “1” by the
start condition detection, and set to “0” by the stop condition detection.
The acknowledgment non-detection interrupt refers to the interrupt that occurs when the SDA terminal
level is detected still staying “H” at the rising edge of the 9th transmission clock. The acknowledgment
detection interrupt refers to the interrupt that occurs when SDA terminal’s level is detected already went
to “L” at the 9th transmission clock. Also, assigning 1 1 0 1 (UART2 reception) to the DMA1 request factor
select bits provides the means to start up the DMA transfer by the effect of acknowledgment detection.
Bit 1 of the UART2 special mode register (037716) is used as the arbitration lost detecting flag control bit.
Arbitration means the act of detecting the nonconformity between transmission data and SDA terminal
data at the timing of the SCL rising edge. This detecting flag is located at bit 11 of the UART2 reception
buffer register, and “1” is set in this flag when nonconformity is detected. Use the arbitration lost detecting
flag control bit to choose which way to use to update the flag, bit by bit or byte by byte. When setting this
bit to “1” and updated the flag byte by byte if nonconformity is detected, the arbitration lost detecting flag
is set to “1” at the falling edge of the 9th transmission clock.
If update the flag byte by byte, must judge and clear (“0”) the arbitration lost detecting flag after complet-
ing the first byte acknowledge detect and before starting the next one byte transmission.
Bit 3 of the UART2 special mode register is used as SCL- and L-synchronous output enable bit. Setting
this bit to “1” goes the P71 data register to “0” in synchronization with the SCL terminal level going to “L”.
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