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The XTAL and X2 pins are associated with analog signals and are not included in the
boundary scan register.
All MC68306 bidirectional pins, except the open-drain I/O pins (HALT, DTACK, BERR, and
RESET ), have a single register bit for pin data and an associated control bit in the
boundary scan register. All open drain I/O pins have a single register bit for pin data and
no associated control bit. To ensure proper operation, the open-drain pins require external
pullups. Twenty-four control bits in the boundary scan register define the output enable
signal for associated groups of bidirectional and three-state pins. The control bits and their
bit positions are listed in Table 7-1.
Name
OPOE3
PPOE8
PPOE9
PPOE10
PPOE11
PPOE12
PPOE13
PPOE14
Boundary scan bit definitions are shown in Table 7-2. The first column in Table 7-2 defines
the bit's ordinal position in the boundary scan register. The shift register bit nearest TDO
(i.e., first to be shifted out) is defined as bit 0; the last bit to be shifted out is bit 123.
The second column references one of the five MC68306 cell types depicted in Figures
7-3–7-7, which describe the cell structure for each type.
The third column lists the pin name for all pin-related bits or defines the name of
bidirectional control register bits.
The last column indicates the associated boundary scan register control bit.
Bidirectional pins include a single scan bit for data (IO.Cell) as depicted in Figure 7-7.
These bits are controlled by one of the two bits shown in Figures 7-5 and 7-6. The value of
the control bit determines whether the bidirectional pin is an input or an output. One or
more bidirectional data bits can be serially connected to a control bit as shown in Figure
7-8. Note that, when sampling the bidirectional data bits, the bit data can be interpreted
only after examining the IO control bit to determine pin direction.
7-4
Table 7-1. Boundary Scan Control Bits
Bit Number
Name
8
PPOE15
12
PPOE0
14
PPOE1
16
PPOE2
18
PPOE3
20
PPOE4
22
PPOE5
24
PPOE6
MC68306 USER'S MANUAL
Bit Number
Name
26
PPOE7
28
DOE
30
HiZ
32
DRAMWOE
34
DRAMOE
36
CPMOE
38
CSOE
40
AOE
Bit Number
42
58
67
86
88
97
100
118
MOTOROLA
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