ATmega64A datasheet(273/392 Pages) ATMEL

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273

8160C–AVR–07/09

ATmega64A

As an example, consider the task of verifying a 1.5V ± 5% input signal at ADC channel 3 when

the power supply is 5.0V and AREF is externally connected to V

CC.

The recommended values from Table 25-5 are used unless other values are given in the algo-

rithm in Table 25-6. Only the DAC and Port Pin values of the Scan-chain are shown. The column

“Actions” describes what JTAG instruction to be used before filling the Boundary-scan Register

with the succeeding columns. The verification should be done on the data scanned out when

scanning in the data on the same row in the table.

Note:

1. Using this algorithm, the timing constraint on the HOLD signal constrains the TCK clock frequency. As the algorithm keeps

HOLD high for five steps, the TCK clock frequency has to be at least five times the number of scan bits divided by the maxi-

mum hold time, t

hold,max.

25.6

ATmega64A Boundary-scan Order

Table 25-7 shows the Scan order between TDI and TDO when the Boundary-scan Chain is

selected as data path. Bit 0 is the LSB; the first bit scanned in, and the first bit scanned out. The

scan order follows the pinout order as far as possible. Therefore, the bits of Port A are scanned

in the opposite bit order of the other ports. Exceptions from the rules are the scan chains for the

analog circuits, which constitute the most significant bits of the scan chain regardless of which

physical pin they are connected to. In Figure 25-3, PXn, Data corresponds to FF0, PXn. Control

The lower limit is:

1024 1.5

V 0,95 5V

⁄

⋅⋅

291

0x123

The upper limit is:

1024 1.5

V 1.05 5V

⁄

⋅⋅

323

0x143

Table 25-6.

Algorithm for Using the ADC

(1)

Ste

Actions

ADCEN

DAC

MUXEN

HOLD

PRECH

PA3.

Data

PA3.

Control

PA3.

Pull-

up_

Enable

SAMPLE_PRELOAD

0x200

0x08

EXTEST

0x200

0x08

0x200

0x08

0x123

0x08

0x123

0x08

Verify the COMP bit scanned out to be 0

0x200

0x08

0x200

0x08

0x200

0x08

0x143

0x08

0x143

0x08

Verify the COMP bit scanned out to be 1

0x200

0x08

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