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4173ES–USB–09/07
AT89C5132 Table 11. Keypad Interface Si gnal Description
Table 12. External Access Signal Description
Table 13. Syst em Signal Description
Signal 
Name Type Description Alternate 
Function
KIN3:0 I Keypad Input Lines 
Holding one of these pins high or low for 24 oscillator periods triggers a 
keypad interrupt. P1.3:0
Signal 
Name Type Description Alternate 
Function
A15:8 I/O Address Lines 
Upper address lines for the external bus. 
Multiplexed higher address and data lines for the IDE interface. P2.7:0
AD7:0 I/O Address/Data Lines 
Multiplexed lower address and data lines for the external memory or the IDE 
interface. P0.7:0
ALE O
Address Latch Enable Output 
ALE signals the start of an external bus cycle and indicates that valid address 
information is available on lines A7:0. An external latch is used to demultiplex 
the address from address/data bus.
-
ISP I/O ISP Enable Input 
This signal must be held to GND through a pull-down resistor at the falling 
reset to force execution of the internal bootloader. -
RD ORead Signal 
Read signal asserted during external data memory read operation. P3.7
WR OWrite Signal 
Write signal asserted during external data memory write operation. P3.6
Signal 
Name Type Description Alternate 
Function
RST  I
Reset Input 
Holding this pin high for 64 oscillator periods while the oscillator is running 
resets the device. The Port pins are driven to their reset conditions when a 
voltage lower than VIL is applied, whether or not the oscillator is running. 
This pin has an internal pull-down resistor which allows the device to be reset 
by connecting a capacitor between this pin and VDD. 
Asserting RST when the chip is in Idle mode or Power-Down mode returns the 
chip to normal operation.
-
TST  I Test I nput  
Test mode entry signal. This pin must be set to VDD.-