STANDARD PRODUCT
PM4351 COMET
DATA SHEET
PMC-1970624
ISSUE 10
COMBINED E1/T1 TRANSCEIVER
PROPRIETARY AND CONFIDENTIAL
351
high causes the COMET to drive the data bus and holding the CSB pin low
tri-states 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 block in the COMET for board
level testing. When IOTST is a logic 1, 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 consequently the device outputs (refer to the
"Test Mode 0 Details" in this section).
HIZIO, HIZDATA:
The HIZIO and HIZDATA bits control the tri-state modes of the COMET .
While the HIZIO bit is a logic 1, all output pins of the COMET except the data
bus are held in a high-impedance state. The microprocessor interface is still
active. While the HIZDATA bit is a logic 1, the data bus is also held in a high-
impedance state which inhibits microprocessor read cycles.
12.1 Test Mode 0
In test mode 0, the COMET allows the logic levels on the device inputs to be
read through the microprocessor interface, and allows the device outputs to be
forced to either logic level through the microprocessor interface.
To enable test mode 0, the IOTST bit in the Master Test Register (register 00BH)
must be set to logic 1 and the following addresses must be written with 00H:
101H, 111H, 115H, 119H, 11DH, 121H, 125H, 129H, 131H, 139H, 141H, 149H,
14DH, 151H, 155H, 157H, 159H, 161H, 165H, 167H, 169H, 16BH, 16DH, 171H,
179H, 181H, 18DH, 191H, 1A9H, 1B1H, 1B9H, 1C1H, 1C9H, 1D1H, 1D7H,
1E1H, 1F1H and 1F9H. All other registers must be in their default (i.e., reset)
state, except as noted below.
Reading the following address locations returns the values for the indicated
inputs:
Table 73
- Observing Inputs in Test Mode 0
Addr
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
114H
RCLKI
1
RDAT
1
118H
TCLKI
2