ST10R272L - DEDICATED PINS
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DEDICATED PINS
Most of the input/output or control signals of the functional the ST10R272L are realized as
alternate functions of pins of the parallel ports. There is, however, a number of signals that
use separate pins, including the oscillator, special control signals and the power supply.
The table below summarizes the dedicated pins of the ST10R272L.
Pin(s)
Function
ALE
Address Latch Enable: controls external address latches that provide a stable
address in multiplexed bus modes. ALE is activated / not activated
RD
External Read Strobe: controls the output drivers of external memory or
peripherals when the ST10R272L reads data from these external devices. Dur-
ing reset and during Hold mode an internal pullup ensures an inactive (high)
level on the RD output.
WR/WRL
External Write/Write Low Strobe: controls the data transfer from the
ST10R272L to an external memory or peripheral device. This pin may either
provide an general WR signal activated for both byte and word write accesses,
or specifically control the low byte of an external 16-bit device (WRL) together
with the signal WRH (alternate function of P3.12/BHE). During reset and during
Hold mode an internal pullup ensures an inactive (high) level on the WR/WRL
output.
READY/READY
Ready Input: receives a control signal from an external memory or peripheral
device that is used to terminate an external bus cycle, provided that this func-
tion is enabled for the current bus cycle. READY/READY may be used as syn-
chronous READY/READY or may be evaluated asynchronously
.
EA
External Access Enable: after reset, this pin sets code access either from the
internal ROM (EA=’1’) or from the external bus interface (EA=’0’).
NMI
Non-Maskable Interrupt Input: triggers a high priority trap via an external signal
(e.g. a power-fail signal). It also serves to validate the PWRDN instruction that
switches the ST10R272L into protected power-down mode
.
RSTIN
Reset Input: puts the ST10R272L into the well defined reset condition either at
power-up or external events like a hardware failure or manual reset. The input
voltage threshold of the RSTIN pin is raised compared to the standard pins in
order to minimize the noise sensitivity of the reset input
.
An internal pullup
resistor permits power on reset using only a capacitor connected to Vss. In
bi-directional reset mode, the RSTIN line is pulled low for the duration of the
internal reset sequence.
Table 24 Summary of dedicated pins