tspc860 ATMEL Corporation, tspc860 Datasheet - Page 26

• Manufacturer Part Number: tspc860
• Description: Integrated Communication Processor
• Manufacturer: ATMEL Corporation

Table 2. Active Pull-Up Resistors Enabled as Outputs
Internal Pull-up and Pull-
down Resistors
Recommended Basic Pin
Connections
Reset Configuration
26
TS, BB
Signal
TA
BI
TSPC860 [Preliminary]
Description
When the TSPC860 is the external bus master throughout the entire bus cycle.
When the TSPC860’s memory controller responds to the access on the external bus, throughout the entire bus cycle.
When the TSPC860’s memory controller responds to the access on the external bus, then:
driven high, then is driven low on cycle n, terminating the bus transaction. External logic can drive TA at any point before
this, thus terminating the cycle early. [For example, assume the GPCM is programmed to drive TA after 15 cycles. If
external logic drives TA before 14 clocks have elapsed then the TA will be accepted by the TSPC860 as a cycle
termination.]
For chip-selects controlled by the GPCM set for external TA, the TSPC860’s TA buffer is not enabled as an output.
For chip-selects controlled by the GPCM set to terminate in n wait-states, TA is enabled as an output on cycle (n-1) and
For chip-selects controlled by the UPM, the TA buffer is enabled as an output throughout the entire bus cycle.
Table 2 summarizes when active pull-up drivers are enabled as outputs.
The purpose of active pull-up buffers is to allow access to zero wait-state logic that
drives a shared signal on the clock cycle immediately following a cycle in which the sig-
nal is driven by the TSPC860. In other words, it eliminates the need for a bus turn-
around cycle.
The TMS and TRST pins have internal pull-up resistors. TSPC860 devices from Rev 0
to Rev A.3 (masks xE64C and xF84C) have an internal pull-up resistor on TCK/DSCK
but no internal pull-up resistor on TDI/DSDI. This was corrected on Rev B and later; on
these chips, the internal pull-up resistor was removed from TCK/DSCK and an internal
pull-up resistor was added to TDI/DSDI.
If RSTCONF is pulled down, during hardware reset (initiated by HRESET or PORE-
SET), the data bus D[0-31] is pulled down with internal pull-down resistors. These
internal pull-down resistors are to provide a logic-zero default for these pins when pro-
gramming the hard reset configuration word. These internal pull-down resistors are
disconnected after HRESET is negated.
No other pins have internal pull-ups or pull-downs.
Resistance values for internal pull-up and pull-down resistors are not specified because
their values may vary due to process variations and shrinks in die size, and they are not
tested. Typical values are on the order of 5 K
of 2.
Some external pin configuration is determined at reset by the hard reset configuration
word. Thus, some decisions as to system configuration (for example, location of BDM
pins) should be made before required application of pull-up and pull-down resistors can
be determined.
RSTCONF should be grounded if the hard reset configuration word is used to configure
the TSPC860 or should be connected to V
Pull-up resistors may not be used on D[0-31] to set the hard reset configuration word, as
the values of the internal pull-down resistors are not specified or guaranteed. To change
a data bus signal from its default logic low state during reset, actively drive that signal
high.
CC
if the default configuration is used.
but can vary by approximately a factor
2129B–HIREL–12/04