AM29240EH AMD [Advanced Micro Devices], AM29240EH Datasheet - Page 14

• Manufacturer Part Number: AM29240EH
• Description: Enhanced High-Performance RISC Microcontrollers
• Manufacturer: AMD [Advanced Micro Devices]

TRIST
Three-State Control
(input, asynchronous, pull-up resistor)
This input is asserted to force all processor outputs into
the high-impedance state. This signal is tied High
through an internal pull-up resistor.
TRST
Test Reset Input
(input, asynchronous, pull-up resistor)
This input asynchronously resets the Test Access Port.
If TRST is not driven, it appears High internally. TRST
must be tied to RESET, even if the Test Access Port is
not being used.
TXDA
Transmit Data, Port A (output, asynchronous)
This output is used to transmit serial data from Serial
Port A.
TXDB
Transmit Data, Port B (output, asynchronous)
This output is used to transmit data from Serial Port B.
This signal is supported on the Am29240EH and
Am29243EH microcontrollers only.
UCLK
UART Clock (input)
This is an oscillator input for generating the UART (Seri-
al Port) clock. To generate the UART clock, the oscillator
frequency may be divided by any amount up to 65,536.
The UART clock operates at 16 times the Serial Port’s
baud rate. As an option, UCLK may be driven with
MEMCLK or INCLK. It can be driven with TTL levels.
VCLK
Video Clock (input, asynchronous)
This clock is used to synchronize the transfer of video
data. As an option, VCLK may be driven with MEMCLK
or INCLK. It can be driven with TTL levels. This signal is
supported on the Am29240EH and Am29245EH mi-
crocontrollers only.
VDAT
Video Data (input/output, synchronous to VCLK)
This is serial data to or from the video device. This signal
is supported on the Am29240EH and Am29245EH mi-
crocontrollers only.
WAIT
Add Wait States
(input, synchronous, internal pull-up)
External accesses are normally timed by the processor.
However, the WAIT signal may be asserted during a PIA,
ROM, or DMA access to extend the access indefinitely.
14
Am29240 EH Microcontroller Series
P R E L I M I N A R Y
For external DMA accesses, the number of wait states
taken by the DRAM controller (this includes peripheral
read and write wait states during DMA transfers) is deter-
mined by the actual value in the DMAWAIT field of the
DMA Control Register or the number of wait states speci-
fied by the IOWAIT field in the PIA Control Register,
whichever is greater.
WARN
Warn (input, asynchronous, edge-sensitive,
internal pull-up)
A High-to-Low transition on this input causes a non-
maskable WARN trap to occur. This trap bypasses the
normal trap vector fetch sequence, and is useful in situa-
tions where the vector fetch may not work (e.g., when
data memory is faulty). This signal has special harden-
ing against metastable states, allowing it to be driven
with a slow-transition-time signal. WARN must be held
active for at least four system clocks for the processor to
recognize it.
WE
Write Enable (output, synchronous)
This signal is used to write the selected DRAM bank.
“Early write” cycles are used so the DRAM data inputs
and outputs can be tied to the common ID Bus.
PRODUCT ENHANCEMENTS
Programmable DRAM Timing
Through Bit 24 in the DRAM Control Register, the DRAM
controller now supports programmable DRAM timing,
for either two- or three-cycle simple accesses, with
single-cycle page-mode accesses. The new bit defined
below.
Bit 24: Programmable DRAM Timing (PDT)—A 1 in
this bit sets the DRAM timing to 2/1, for two-cycle simple
accesses and single-cycle page-mode accesses. A 0 in
this bit sets the DRAM timing to 3/1, for three-cycle sim-
ple accesses and single-cycle page-mode accesses.
FEATURES NO LONGER SUPPORTED
The following features are no longer supported on the
Am29240EH, Am29245EH, and Am29243EH micro-
controllers:
33 MHz operating frequency
Scalable Clocking
turbo mode or clock doubling)
16-bit DRAM memory
MEMDRV signal
MEMCLK as an input
technology (also known as