Signal and Transistor Descriptions
ARM DDI 0210C Copyright © 2001, 2004 ARM Limited. All rights reserved. A-7
DOUT[31:0]
Data output bus
O Unidirectional bus used to transfer data from the processor to the memory
system.
This bus is only used when BUSEN is HIGH. Otherwise it is driven to a
value of zero.
During write cycles the output data becomes valid while MCLK is LOW,
and remains valid until after the falling edge of MCLK.
DRIVEBS
Boundary scan cell enable
O Controls the multiplexors in the scan cells of an external boundary-scan
chain.
This must be left unconnected, if an external boundary-scan chain is not
connected.
ECAPCLK
EXTEST capture clock
O Only used on the ARM7TDMI test chip, and must otherwise be left
unconnected.
ECAPCLKBS
EXTEST capture clock for
boundary-scan
O Used to capture the device inputs of an external boundary-scan chain during
EXTEST.
When scan chain 3 is selected, the current instruction is EXTEST and the
TAP controller state machine is in the CAPTURE- DR state, then this signal
is a pulse equal in width to TCK2.
This must be left unconnected, if an external boundary-scan chain is not
connected.
ECLK
External clock output
O In normal operation, this is simply MCLK, optionally stretched with
nWAIT, exported from the core. When the core is being debugged, this is
DCLK, which is generated internally from TCK.
EXTERN0
External input 0
IC This is connected to the EmbeddedICE-RT logic and enables breakpoints
and watchpoints to be dependent on an external condition.
EXTERN1
External input 1
IC This is connected to the EmbeddedICE-RT logic and enables breakpoints
and watchpoints to be dependent on an external condition.
HIGHZ
High impedance
O When the HIGHZ instruction has been loaded into the TAP controller this
signal is HIGH.
See Appendix B Debug in Depth for details.
ICAPCLKBS
INTEST capture clock
O This is used to capture the device outputs in an external boundary-scan chain
during INTEST.
This must be left unconnected, if an external boundary-scan chain is not
connected.
Table A-3 Signal descriptions (continued)
Name Type Description
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