AT80C32X2 View Datasheet(PDF) - Atmel Corporation
Part Name
Description
MFG CO.
'AT80C32X2' PDF : 55 Pages View PDF
ONCETM Mode (ON Chip
Emulation)
The ONCE mode facilitates testing and debugging of systems using TS80C52X2 with-
out removing the circuit from the board. The ONCE mode is invoked by driving certain
pins of the TS80C52X2; the following sequence must be exercised:
• Pull ALE low while the device is in reset (RST high) and PSEN is high.
• Hold ALE low as RST is deactivated.
While the TS80C52X2 is in ONCE mode, an emulator or test CPU can be used to drive
the circuit Table 26. shows the status of the port pins during ONCE mode.
Normal operation is restored when normal reset is applied.
Table 16. External Pin Status during ONCE Mode
ALE
Weak pull-
up
PSEN
Weak pull-
up
Port 0
Float
Port 1
Weak pull-
up
Port 2
Weak pull-
up
Port 3
Weak pull-
up
XTAL1/2
Active
28 TS8xCx2X2
4184I–8051–02/08
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