HPC16004 datasheet(16/36 Pages) NSC

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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 IO 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

TLDD11372 13

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

EXM

Memory

Mode

Bit

Configuration

Single-Chip Normal

C000FFFF on-chip

Expanded Normal

C000FFFF on-chip

0300BFFF off-chip

Single-Chip ROMless

C000FFFF off-chip

Expanded ROMless

0300FFFF off-chip

Note

In all operating modes the on-chip RAM and Registers (000002FF)

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

TLDD11372 14

FIGURE 16 8-Bit External Memory

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