
DS3112
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2.9 JTAG
Signal
Description
Signal Name:
JTCLK
Signal Description:
JTAG IEEE 1149.1 Test Serial Clock
Signal Type:
Input
This signal is used to shift data into JTDI on the rising edge and out of JTDO on the falling edge. If not
used, this signal should be pulled high.
Signal Name:
JTDI
Signal Description:
JTAG IEEE 1149.1 Test Serial Data Input
Signal Type:
Input (with internal 10k
Ω
pullup)
Test instructions and data are clocked into this signal on the rising edge of JTCLK. If not used, this signal
should be pulled high. This signal has an internal pullup.
Signal Name:
JTDO
Signal Description:
JTAG IEEE 1149.1 Test Serial Data Output
Signal Type:
Output
Test instructions are clocked out of this signal on the falling edge of JTCLK. If not used, this signal
should be left open circuited.
Signal Name:
JTRST
Signal Description:
JTAG IEEE 1149.1 Test Reset
Signal Type:
Input (with internal 10k
Ω
pullup)
This signal is used to asynchronously reset the test access port controller. At power-up,
JTRST
must be
set low and then high. This action will set the device into the boundary scan bypass mode allowing
normal device operation. If boundary scan is not used, this signal should be held low. This signal has an
internal pullup.
Signal Name:
JTMS
Signal Description:
JTAG IEEE 1149.1 Test Mode Select
Signal Type:
Input (with internal 10k
Ω
pullup)
This signal is sampled on the rising edge of JTCLK and is used to place the test port into the various
defined IEEE 1149.1 states. If not used, this signal should be pulled high. This signal has an internal
pullup.
2.10 Supply, Test, Reset, and Mode Signal Description
Signal Name:
RST*
Signal Description:
Global Hardware Reset
Signal Type:
Input (with internal 10k
Ω
pullup)
This active low asynchronous signal causes the device to be reset. When this signal is forced low, it
causes all of the internal registers to be forced to 00h and the high-speed T3/E3 ports as well as the low-
speed T1/E1 ports to source an unframed all ones data pattern. The device will be held in a reset state as
long as this signal is low. This signal should be activated after the hardware configuration signals (LIEN
and T3E3MS) and the clocks (FTCLK, LTCLK, HRCLK, and LITCLK) are stable and must be returned
high before the device can be configured for operation.