PIC24FJ128GA310 datasheet(235/406 Pages) MICROCHIP

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DS39996F-page 235

PIC24FJ128GA310 FAMILY

17.2

Setting Baud Rate When

Operating as a Bus Master

To compute the Baud Rate Generator reload value, use

Equation 17-1.

EQUATION 17-1:

COMPUTING BAUD RATE

RELOAD VALUE(1,2)

17.3

Slave Address Masking

The I2CxMSK register (Register 17-3) designates

address bit positions as “don’t care” for both 7-Bit and

10-Bit Addressing modes. Setting a particular bit loca-

tion (= 1) in the I2CxMSK register causes the slave

module to respond whether the corresponding address

bit value is a ‘0’ or a ‘1’. For example, when I2CxMSK

is set to ‘00100000’, the slave module will detect both

addresses, ‘0000000’ and ‘0100000’.

To enable address masking, the Intelligent Peripheral

Management Interface (IPMI) must be disabled by

clearing the IPMIEN bit (I2CxCON<11>).

TABLE 17-2:

I2C™ RESERVED ADDRESSES(1)

Note 1:

Based on FCY = FOSC/2; Doze mode and

PLL are disabled.

These clock rate values are for guidance

only. The actual clock rate can be affected

by various system level parameters. The

actual clock rate should be measured in

its intended application.

FSCL =

FCY

I2CxBRG + 1 +

FCY

10,000,000

I2CxBRG =

FCY

10,000,000

FCY

FSCL

–– 1

or:

(

)

Note:

As a result of changes in the I2C™ proto-

col, the addresses in Table 17-2 are

reserved and will not be Acknowledged in

Slave mode. This includes any address

mask settings that include any of these

addresses.

TABLE 17-1:

I2C™ CLOCK RATES(1,2)

Required System FSCL

FCY

I2CxBRG Value

Actual FSCL

(Decimal)

(Hexadecimal)

100 kHz

16 MHz

157

100 kHz

8 MHz

100 kHz

4 MHz

99 kHz

400 kHz

16 MHz

404 kHz

400 kHz

8 MHz

404 kHz

400 kHz

4 MHz

385 kHz

400 kHz

2 MHz

385 kHz

1 MHz

16 MHz

1.026 MHz

1 MHz

8MHz

1.026MHz

1 MHz

4MHz

0.909MHz

Note 1:

Based on FCY = FOSC/2; Doze mode and PLL are disabled.

These clock rate values are for guidance only. The actual clock rate can be affected by various system

level parameters. The actual clock rate should be measured in its intended application.

Slave Address

R/W Bit

Description

0000 000

General Call Address(2)

0000 000

Start Byte

0000 001

CBus Address

0000 01x

Reserved

0000 1xx

HS Mode Master Code

1111 0xx

10-Bit Slave Upper Byte(3)

1111 1xx

Reserved

Note 1:

The address bits listed here will never cause an address match, independent of address mask settings.

The address will be Acknowledged only if GCEN = 1.

A match on this address can only occur on the upper byte in 10-Bit Addressing mode.

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