sae81c80a Infineon Technologies Corporation, sae81c80a Datasheet - Page 8

• Manufacturer Part Number: sae81c80a
• Description: Cmos Dual-port Ram
• Manufacturer: Infineon Technologies Corporation

SAE 81C80 A
Chip-Select Inputs
The chip-select inputs affect signals WR and RD, but not the ALE input. Therefore, the
ALE signal on the DPR (even if the DPR is not selected) must correspond to the
specified values. To eliminate selection, it is sufficient if one of the two chip-select inputs
becomes inactive when the falling edge of WR or RD appears.
Reset
The reset is necessary for setting the control units of the DPR to a defined initial state.
It initializes the timer-mode registers with the values 0000XXX0
(timers 1 and 2) and
B
00000XX0
(timer 3). The INT outputs are set to 0.
B
The reset input is a TTL input without Schmitt-trigger response. For this reason, neither
an ALE nor a WR signal must be applied to the DPR if the voltage on the reset input is
V
below
. The length of the Reset pulse must be greater than six clock (oscillator) cycles
IH
and the clock must be active.
When the reset input is low the reset input is low, outputs WD1, WD2 and WD3 are set
to low. After a reset these outputs are high. The scheduling registers are set to state 1
by reset.
A reset is also necessary if the DPR is reactivated from power-down, while the contents
of the RAM and oscillator remain unaffected.
Power-Down Mode
When the power-down mode (PD) is activated, all inputs (except PD and XTAL1,
XTAL2) plus the oscillator are disabled. This means that any levels are possible on the
remaining inputs.
An active level on PD also produces an internal reset. Nevertheless, to ensure proper
operation after deactivation of the power-down mode, an external reset should be made
to bridge the time required by the oscillator for buildup. The outputs of the ports go high-
impedance, while outputs CLKO, WDO, WD1, WD2, WD3, INT1, INT2 and INT3 are set
to low. The PD input shows a Schmitt-trigger response. This allows
V
to be evaluated
DD
directly, for example (see application circuit).
Semiconductor Group
8