Texas Instruments TMS320C642X manual 2 10-Bit Addressing Format, Free Data Format, Ack

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2.6.210-Bit Addressing Format

The 10-bit addressing format (Figure 9) is like the 7-bit addressing format, but the master sends the slave address in two separate byte transfers. The first byte consists of 11110b, the two MSBs of the 10-bit slave address, and R/W = 0 (write). The second byte is the remaining 8 bits of the 10-bit slave address. The slave must send acknowledgment (ACK) after each of the two byte transfers. Once the master has written the second byte to the slave, the master can either write data or use a repeated START condition to change the data direction. (For more information about using 10-bit addressing, see the Philips Semiconductors I2C-bus specification.)

Write 1 to the XA bit of ICMDR to select the 10-bit addressing format.

Figure 9. I2C Peripheral 10-Bit Addressing Format With Master-Transmitter Writing to Slave-Receiver

(FDF = 0, XA = 1 in ICMDR)

1

7

1

1

8

1

n

1

1

S

1 1 1 1 0 A A

0

ACK

A A A A A A A A

ACK

Data

ACK P

A A = 2 MSBs

R/W

8 LSBs of slave address

n = The number of data bits (from 1 to 8) specified by the bit count (BC) field of ICMDR.

2.6.3Free Data Format

In the free data format (Figure 10), the first bits after a START condition (S) are a data word. An ACK bit is inserted after each data word, which can be from 1 to 8 bits, depending on the bit count (BC) bits of ICMDR. No address or data-direction bit is sent. Therefore, the transmitter and the receiver must both support the free data format, and the direction of the data must be constant throughout the transfer.

To select the free data format, write 1 to the free data format (FDF) bit of ICMDR.

Figure 10. I2C Peripheral Free Data Format (FDF = 1 in ICMDR)

1

n

1

n

1

n

1

1

S

Data

ACK

Data

ACK

Data

ACK P

n = The number of data bits (from 1 to 8) specified by the bit count (BC) field of ICMDR.

2.6.4Using a Repeated START Condition

The repeated START condition can be used with the 7-bit addressing, 10-bit addressing, and free data formats. The 7-bit addressing format using a repeated START condition (S) is shown in Figure 11. At the end of each data word, the master can drive another START condition. Using this capability, a master can transmit/receive any number of data words before driving a STOP condition. The length of a data word can be from 1 to 8 bits and is selected with the bit count (BC) bits of ICMDR.

Figure 11. I2C Peripheral 7-Bit Addressing Format With Repeated START Condition

(FDF = 0, XA = 0 in ICMDR)

1	7	1	1	n	1	1	7	1	1	n	1	1
S	Slave address	R/W	ACK	Data	ACK	S	Slave address	R/W	ACK	Data	ACK	P

1	Any	1
	number

n = The number of data bits (from 1 to 8) specified by the bit count (BC) field of ICMDR.

Any number

14	Inter-Integrated Circuit (I2C) Peripheral	SPRUEN0D –March 2011
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