HPC16064 Datasheet, PDF (16/36 Pages) National Semiconductor (TI) – High-Performance microController

HPC46064 Operating Modes
SINGLE CHIP NORMAL MODE
In this mode the HPC46064 functions as a self-contained
microcomputer (see Figure 15 ) with all memory (RAM and
ROM) on-chip It can address internal memory only consist-
ing of 16k bytes of ROM (C000 to FFFF) and 512 bytes of
on-chip RAM and Registers (0000 to 02FF) The ‘‘illegal
address detection’’ feature of the WATCHDOG is enabled
in the Single-Chip Normal mode and a WATCHDOG Output
(WO) will occur if an attempt is made to access addresses
that are outside of the on-chip ROM and RAM range of the
device Ports A and B are used for I O functions and not for
addressing external memory The EXM pin and the EA bit of
the PSW register must both be logic ‘‘0’’ to enter the Single-
Chip Normal mode
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FIGURE 15 Single-Chip Mode
EXPANDED NORMAL MODE
The Expanded Normal mode of operation enables the
HPC46064 to address external memory in addition to the
on-chip ROM and RAM (see Table I) WATCHDOG illegal
address detection is disabled and memory accesses may
be made anywhere in the 64k byte address range without
triggering an illegal address condition The Expanded Nor-
mal mode is entered with the EXM pin pulled low (logic ‘‘0’’)
and setting the EA bit in the PSW register to ‘‘1’’
SINGLE-CHIP ROMLESS MODE
In this mode the on-chip mask programmed ROM of the
HPC46064 is not used The address space corresponding
to the on-chip ROM is mapped into external memory so 16k
of external memory may be used with the HPC46064 (see
Table I) The WATCHDOG circuitry detects illegal address-
es (addresses not within the on-chip ROM and RAM range)
The Single-Chip ROMless mode is entered when the EXM
pin is pulled high (logic ‘‘1’’) and the EA bit is logic ‘‘0’’
TABLE I HPC46064 Operating Modes
Operating
Mode
EXM EA
Pin Bit
Memory
Configuration
Single-Chip Normal
0 0 C000 FFFF on-chip
Expanded Normal
0 1 C000 FFFF on-chip
0300 BFFF off-chip
Single-Chip ROMless 1 0 C000 FFFF off-chip
Expanded ROMless
1 1 0300 FFFF off-chip
Note In all operating modes the on-chip RAM and Registers (0000 02FF)
may be accessed
EXPANDED ROMLESS MODE
This mode of operation is similar to Single-Chip ROMless
mode in that no on-chip ROM is used however a full 64k
bytes of external memory may be used The ‘‘illegal address
detection’’ feature of WATCHDOG is disabled The EXM pin
must be pulled high (logic ‘‘1’’) and the EA bit in the PSW
register set to ‘‘1’’ to enter this mode
FIGURE 16 8-Bit External Memory
16
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