M37221M4H_15 Datasheet, PDF (36/114 Pages) Renesas Technology Corp – SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER for VOLTAGE SYNTHESIZER with ON-SCREEN DISPLAY CONTROLLER

M37221M4H/M6H/M8H/MAH–XXXSP/FP M37221EASP/FP
8.6.3 I²C Clock Control Register
The I²C clock control register (address 00DB16) is used to set ACK
control, SCL mode and SCL frequency.
(1) Bits 0 to 4: SCL frequency control bits (CCR0–CCR4)
These bits control the SCL frequency.
(2) Bit 5: SCL mode specification bit (FAST MODE)
This bit specifies the SCL mode. When this bit is set to “0,” the stan-
dard clock mode is set. When the bit is set to “1,” the high-speed
clock mode is set.
(3) Bit 6: ACK bit (ACK BIT)
This bit sets the SDA status when an ACK clock^✽ is generated. When
this bit is set to “0,” the ACK return mode is set and SDA goes to
LOW at the occurrence of an ACK clock. When the bit is set to “1,”
the ACK non-return mode is set. The SDA is held in the HIGH status
at the occurrence of an ACK clock.
However, when the slave address matches the address data in the
reception of address data at ACK BIT = “0,” the SDA is automatically
made LOW (ACK is returned). If there is a mismatch between the
slave address and the address data, the SDA is automatically made
HIGH (ACK is not returned).
✽ACK clock: Clock for acknowledgement
(4) Bit 7: ACK clock bit (ACK)
This bit specifies a mode of acknowledgment which is an acknowl-
edgment response of data transmission. When this bit is set to “0,”
the no ACK clock mode is set. In this case, no ACK clock occurs
after data transmission. When the bit is set to “1,” the ACK clock
mode is set and the master generates an ACK clock upon comple-
tion of each 1-byte data transmission.The device for transmitting
address data and control data releases the SDA at the occurrence of
an ACK clock (make SDA HIGH) and receives the ACK bit generated
by the data receiving device.
Note: Do not write data into the I²C clock control register during transmission.
If data is written during transmission, the I²C clock generator is reset, so
that data cannot be transmitted normally.
I²C Clock Control Register
b7 b6 b5 b4 b3 b2 b1 b0
I²C clock control register (S2) [Address 00DB16]
B
Name
Functions
After reset R W
0 SCL frequency control bits _{Setup value of Standard clock High speed}
0
to (CCR0 to CCR4)
CCR4–CCR0 mode clock mode
4
00 to 02 Setup disabled Setup disabled
03
Setup disabled ³³³
04
Setup disabled ²⁵⁰
05
100 400 (See note)
06
83.3
166
5 SCL mode
specification bit
(FAST MODE)
500/CCR value 1000/CCR value
1D
17.2
34.5
1E
16.6
33.3
1F
16.1
32.3
(at φ = 4 MHz, unit : kHz)
0: Standard clock mode
0
1: High-speed clock mode
6 ACK bit
0: ACK is returned.
0
(ACK BIT)
1: ACK is not returned.
RW
RW
RW
7 ACK clock bit
(ACK)
0: No ACK clock
1: ACK clock
0 _RW
Note: At 400 kHz in the high-speed clock mode, the duty is as below .
“0” period : “1” period = 3 : 2
In the other cases, the duty is as below.
“0” period : “1” period = 1 : 1
Fig. 8.6.4 I²C Address Register
Rev.1.00 Oct 01, 2002 page 34 of 110
REJ03B0134-0100Z