IEEE 1149.1 Test Access Port
9-4
MC68307 USER’S MANUAL
MOTOROLA
9.3 BOUNDARY SCAN REGISTER
The MC68307 IEEE 1149.1 implementation has a 124-bit boundary scan register. This reg-
ister contains bits for all device signal and clock pins and associated control signals. The
XTAL, EXTAL and RSTIN pins are associated with analog signals and are not included in
the boundary scan register.
All MC68307 bidirectional pins, except the open-drain I/O pins (HALT, DTACK, RESET,
SCL and SDA), have a register bit for the output path and another for the input path. In addi-
tion, SCL and SDA have a third bit which controls these pins. 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. Thirty-two 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 9-1.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 116.
The second column references one of the five MC68307 cell types depicted in
Figure 9-3 to
Figure 9-7, 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 9-7. These
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 9-8. 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.
Table 9-1. Boundary Scan Control Bits
Name
Bit Number
Name
Bit Number
Name
Bit Number
Name
Bit Number
bus.ctl
3
pa3.ctl
57
pb11.ctl
73
pb3.ctl
89
rw.ctl
10
pa2.ctl
59
pb10.ctl
75
pb2.ctl
91
adb.ctl
21
pa1.ctl
61
pb9.ctl
77
pb1.pu
93
ab.ctl
46
pa0.ctl
63
pb8.ctl
79
pb1.ctl
94
pa7.ctl
49
pb15.ctl
65
pb7.ctl
81
pb0.pu
96
pa6.ctl
51
pb14.ctl
67
pb6.ctl
83
pb0.ctl
97
pa5.ctl
53
pb13.ctl
69
pb5.ctl
85
dhi.ctl
99
pa4.ctl
55
pb12.ctl
71
pb4.ctl
87
dlo.ctl
108