PM4314 QDSX
DATA SHEET
PMC-950857
ISSUE 5
QUAD T1/E1 LINE INTERFACE DEVICE
DBCTRL:
The DBCTRL bit is used to pass control of the data bus drivers to the CSB
pin. When the DBCTRL bit is set to logic one and either IOTST or PMCTST
are logic one, the CSB pin controls the output enable for the data bus. While
the DBCTRL bit is set, holding the CSB pin high (IOTST must be set to logic
1 since CSB high resets PMCTST) causes the QDSX to drive the data bus
and holding the CSB pin low tristates the data bus. The DBCTRL bit
overrides the HIZDATA bit. The DBCTRL bit is used to measure the drive
capability of the data bus driver pads.
IOTST:
The IOTST bit is used to allow normal microprocessor access to the test
registers and control the test mode in each TSB block in the QDSX for board
level testing. When IOTST is a logic one, all blocks are held in test mode and
the microprocessor may write to a block's test mode 0 registers to manipulate
the outputs of the block and consequentially the device outputs (refer to the
"Test Mode 0 Details" in the "Test Features" section). The IOTST bit is also
used in conjunction with the HWTST bit as described below.
HIZIO, HIZDATA:
The HIZIO and HIZDATA bits control the tristate modes of the QDSX. While
the HIZIO bit is a logic one, all output pins of the QDSX except the data bus
and output TDO are held tristate. The microprocessor interface is still active.
While the HIZDATA bit is a logic one, the data bus is also held in a high-
impedance state which inhibits microprocessor read cycles. The HIZDATA bit
is overridden by the DBCTRL bit.
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
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PMC [ PMC-SIERRA, INC ]
