ATMEGA640 datasheet(228/436 Pages) MICROCHIP

228 / 436 page

228

ATmega640/V-1280/V-1281/V-2560/V-2561/V [DATASHEET]

DS40002211A

correctly. Preferably the DDR_XCKn should be set up before the USART in MSPIM is enabled (that is, TXENn and

RXENn bit set to one).

The internal clock generation used in MSPIM mode is identical to the USART synchronous master mode. The

baud rate or UBRRn setting can therefore be calculated using the same equations, see Table 23-1.

Note:

1. The baud rate is defined to be the transfer rate in bit per second (bps).

BAUD

Baud rate (in bits per second, bps).

fOSC

System Oscillator clock frequency.

UBRRn

Contents of the UBRRnH and UBRRnL Registers, (0-4095).

23.3 SPI Data Modes and Timing

There are four combinations of XCKn (SCK) phase and polarity with respect to serial data, which are determined

by control bits UCPHAn and UCPOLn. The data transfer timing diagrams are shown in Figure 23-1. Data bits are

shifted out and latched in on opposite edges of the XCKn signal, ensuring sufficient time for data signals to stabi-

lize. The UCPOLn and UCPHAn functionality is summarized in Table 23-2. Note that changing the setting of any of

these bits will corrupt all ongoing communication for both the Receiver and Transmitter.

Figure 23-1. UCPHAn and UCPOLn data transfer timing diagrams.

Table 23-1.

Equations for Calculating Baud Rate Register Setting

Operating Mode

Equation for Calculating Baud Rate(1)

Equation for Calculating UBRRn Value

Synchronous Master mode

BAUD

fOSC

2 UBRRn 1



---------------------------------------

UBRRn

fOSC

2BAUD

-------------------- 1

–

Table 23-2.

UCPOLn and UCPHAn Functionality.

UCPOLn

UCPHAn

SPI Mode

Leading Edge

Trailing Edge

Sample (Rising)

Setup (Falling)

Setup (Rising)

Sample (Falling)

Setup (Rising)

Setup (Falling)

Sample (Rising)

XCK

Data setup (TXD)

Data sample (RXD)

XCK

Data setup (TXD)

Data sample (RXD)

XCK

Data setup (TXD)

Data sample (RXD)

XCK

Data setup (TXD)

Data sample (RXD)

UCPOL=0

UCPOL=1

ATMEGA640 Datasheet(PDF) 228 Page - Microchip Technology

ATMEGA640 Datasheet(HTML) 228 Page - Microchip Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL