M37281MAH–XXXSP,M37281MFH–XXXSP,M37281MKH–XXXSP, M37281EKSP
Rev.1.01 2003.07.16 page 36 of 170
8.6.3 I
2
C Clock Control Register
The I
2
C clock control register (address 00FA
16
) 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
Fig. 8.6.4 I
2
C Clock Control
(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 I
2
C clock control register during transmission.
If data is written during transmission, the I
2
C clock generator is reset, so
that data cannot be transmitted normally.
b7 b6 b5 b4 b3 b2 b1 b0
I
2
C clock control register (S2) [Address 00FA
16
]
I
2
C Clock Control Register
0
to
4
SCL frequency control bits
(CCR0 to CCR4)
7
5
6
SCL mode
specification bit
(FAST MODE)
0: Standard clock mode
1: High-speed clock mode
0
Standard
clock mode
B
Name
Functions
After reset R W
0
0
0
ACK bit
(ACK BIT)
ACK clock bit
(ACK)
0: ACK is returned.
1: ACK is not returned.
0: No ACK clock
1: ACK clock
High speed
clock mode
Setup disabledSetup disabled
Setup disabled
Setup disabled
00 to 02
333
250
03
04
05
06
100
83.3
400 (See note)
166
500/CCR value
17.2
16.6
16.1
(at f = 4 MHz, unit : kHz)
1000/CCR value
34.5
33.3
32.3
.
1D
1E
1F
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
Register
value
b4 to b0
R W
R W
R W
R W