HPC16003 datasheet(17/36 Pages) NSC

17 / 36 page

HPC16003 Operating Modes

EXPANDED ROMLESS MODE (HPC16003)

Because the HPC16003 has no on-chip ROM it has only

one mode of operation the Expanded ROMless Mode The

EXM pin must be pulled high (logic ‘‘1’’) on power up the

EA bit in the PSW register should be set to a ‘‘1’’ The

HPC16003 is a ROMless device and is intended for use with

external memory The external memory may be any combi-

nation of ROM and RAM Up to 64k bytes of external mem-

ory may be accessed It is necessary to vector on reset to

an address between F000 and FFFF therefore the user

should have external memory at these addresses The EA

bit in the PSW register must immediately be set to ‘‘1’’ at the

beginning of the user’s program to disable illegal address

detection in the WATCHDOG logic

TABLE II HPC16003 Operating Modes

Operating

EXM

Memory

Mode

Bit

Configuration

Expanded ROMless

0200FFFF off-chip

Note

The on-chip RAM and Registers (000001FF) of the HPC16003 may

be accessed at all times

TLDD8801 – 17

FIGURE 15 Single-Chip Mode

TLDD8801 – 18

FIGURE 16 8-Bit External Memory

HPC16003 Datasheet(PDF) 17 Page - National Semiconductor (TI)