M38045FBHKP datasheet(64/116 Pages) RENESAS

64 / 116 page

Rev.1.01

Jan 25, 2005

page 64 of 114

REJ03B0131-0101Z

3804 Group (Spec. H)

Fig. 61 Interrupt request signal generating timing

Fig. 60 Structure of I2C status register

•Bit 6: Communication mode specification bit (transfer direc-

tion specification bit: TRX)

This bit decides a direction of transfer for data communication.

When this bit is “0,” the reception mode is selected and the data of

a transmitting device is received. When the bit is “1,” the transmis-

sion mode is selected and address data and control data are

output onto the SDA in synchronization with the clock generated

on the SCL.

This bit is set/reset by software and hardware. About set/reset by

hardware is described below. This bit is set to “1” by hardware

when all the following conditions are satisfied:

• When ALS is “0”

• In the slave reception mode or the slave transmission mode

• When the R/W bit reception is “1”

This bit is set to “0” in one of the following conditions:

• When arbitration lost is detected.

• When a STOP condition is detected.

• When writing “1” to this bit by software is invalid by the START

condition duplication preventing function (Note).

• With MST = “0” and when a START condition is detected.

• With MST = “0” and when ACK non-return is detected.

• At reset

•Bit 7: Communication mode specification bit (master/slave

specification bit: MST)

This bit is used for master/slave specification for data communica-

tion. When this bit is “0,” the slave is specified, so that a START

condition and a STOP condition generated by the master are re-

ceived, and data communication is performed in synchronization

with the clock generated by the master. When this bit is “1,” the

master is specified and a START condition and a STOP condition

are generated. Additionally, the clocks required for data communi-

cation are generated on the SCL.

This bit is set to “0” in one of the following conditions.

• Immediately after completion of the byte which has lost arbitra-

tion when arbitration lost is detected

• When a STOP condition is detected.

• Writing “1” to this bit by software is invalid by the START condi-

tion duplication preventing function (Note).

• At reset

Note: START condition duplication preventing function

The MST, TRX, and BB bits is set to “1” at the same time after con-

firming that the BB flag is “0” in the procedure of a START condition

occurrence. However, when a START condition by another master

device occurs and the BB flag is set to “1” immediately after the con-

tents of the BB flag is confirmed, the START condition duplication

preventing function makes the writing to the MST and TRX bits in-

valid. The duplication preventing function becomes valid from the

rising of the BB flag to reception completion of slave address.

MST

I2C status register

(S1 : address 001316)

Last receive bit (Note)

0 :Last bit = “0”

1 :Last bit = “1”

General call detecting flag

(Note)

0 :No general call detected

1 :General call detected

Slave address comparison flag

(Note)

0 : Address disagreement

1 : Address agreement

Arbitration lost detecting flag

(Note)

0 : Not detected

1 : Detected

SCL pin low hold bit

0 : SCL pin low hold

1 : SCL pin low release

Bus busy flag

0 : Bus free

1 : Bus busy

Communication mode

specification bits

00 : Slave receive mode

01 : Slave transmit mode

10 : Master receive mode

11 : Master transmit mode

TRX BB PIN AL AAS AD0 LRB

Note: These bits and flags can be read out, but cannot be written.

Write “0” to these bits at writing.

SCL

I2CIRQ

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