IAR SYSTEMS I-jet User Manual page 18

Adapters
I-jet®
18
User Guide
These are the pin definitions of the ARM-20 adapter:
I-jet
Pin Name
direction
nTRST Output Test Reset
TCK Output Test Clock
TMS Output Test Mode Select TMS controls transitions in the tap controller state
TDI Output Test Data Input
TDO Input Test Data Output TDO is the return path of the test data input signal
RTCK Input TCK Return
Table 6: ARM-20 pin definitions
Description
Active LOW signal that resets the TAP controller's
state machine.
TCK synchronizes all JTAG transactions. TCK
connects to all JTAG devices in the scan chain. TCK
flows down the stack of modules and connects to
each JTAG device. However, if there is a device in the
scan chain that synchronizes TCK to some other
clock, then all down-stream devices are connected to
the RTCK signal on that processor.
machine. TMS connects to all JTAG devices in the
scan chain as the signal flows down the module stack.
TDI is the test data input signal that is routed to the
TDI input of the first device in the scan chain.
TDI. In a multi-device JTAG chain, the TDO of the
first device connects to the TDI of the next device,
etc. The last device's TDO is connected to the TDO
on the JTAG header.
RTCK is a mechanism for returning the sampled
clock to the JTAG equipment, so that the clock is not
advanced until the synchronizing device captured the
data. In adaptive clocking mode, I-jet is required to
detect an edge on RTCK before changing TCK. In a
multi-device JTAG chain, the RTCK output from a
device connects to the TCK input of the
down-stream device.
If there are no synchronizing devices in the scan
chain, it is unnecessary to use the RTCK signal and it
is connected to ground on the target board.