Rainbow Electronics ATmega128L - Manual (Page 258)

258
ATmega128(L)
2467B–09/01
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 maximum hold time,
t
hold,max
ATmega128 Boundary-
scan Order Table 107 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 pin-out order as far as possible. Therefore, the
bits of Port A is 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
123, PXn. Data corresponds to FF0, PXn. Control corresponds to FF1, and PXn.
Pullup_enable corresponds to FF2. Bit 2, 3, 4, and 5 of Port C is not in the scan chain,
since these pins constitute the TAP pins when the JTAG is enabled.
6
Verify the
COMP bit
scanned
out to be 0
1 0x200 0x08 1 1 0 0 0
7 1 0x200 0x08 0 1 0 0 0
8 1 0x200 0x08 1 1 0 0 0
9 1 0x143 0x08 1 1 0 0 0
10 1 0x143 0x08 1 0 0 0 0
11
Verify the
COMP bit
scanned
out to be 1
1 0x200 0x08 1 1 0 0 0
Table 106. Algorithm for Using the ADC
Step Actions ADCEN DAC MUXEN HOLD PRECH
PA3.
Data PA3.
Control
PA3.
Pullup_
Enable
Table 107. ATmega128 Boundary-scan Order
Bit Number Signal Name Module
204 AC_IDLE Comparator
203 ACO
202 ACME
201 AINBG