ATmega16A datasheet(236/352 Pages) ATMEL

236 / 352 page

236

8154B–AVR–07/09

ATmega16A

The Boundary-scan logic is not included in the figures in the datasheet. Figure 24-4 shows a

simple digital Port Pin as described in the section “I/O Ports” on page 49. The Boundary-scan

details from Figure 24-3 replaces the dashed box in Figure 24-4.

When no alternate port function is present, the Input Data – ID – corresponds to the PINxn Reg-

ister value (but ID has no synchronizer), Output Data corresponds to the PORT Register, Output

Control corresponds to the Data Direction – DD Register, and the Pull-up Enable – PUExn – cor-

responds to logic expression PUD · DDxn · PORTxn.

Digital alternate port functions are connected outside the dotted box in Figure 24-4 to make the

scan chain read the actual pin value. For Analog function, there is a direct connection from the

external pin to the analog circuit, and a scan chain is inserted on the interface between the digi-

tal logic and the analog circuitry.

Figure 24-3. Boundary-scan Cell for Bidirectional Port Pin with Pull-up Function.

Port Pin (PXn)

Vcc

EXTEST

To Next Cell

ShiftDR

Output Control (OC)

Pullup Enable (PUE)

Output Data (OD)

Input Data (ID)

From Last Cell

UpdateDR

ClockDR

FF2

LD2

FF1

LD1

LD0

FF0

ATmega16A Datasheet(PDF) 236 Page - ATMEL Corporation