MC68HC711D3_05 Datasheet, PDF (31/138 Pages) Freescale Semiconductor, Inc – Microcontrollers

Programmable Read-Only Memory (PROM)
ROMON — PROM Enable Bit
This bit is set out of reset, enabling the EPROM or OTPROM in all modes. This bit is writable once in
normal modes (SMOD = 0), but is writable at any time in special modes (SMOD = 1).
1 = PROM is present in the memory map.
0 = PROM is disabled from the memory map.
NOTE
In expanded mode out of reset, the EPROM or OTPROM is located at
$7000–$7FFF. In all other modes, the PROM resides at $F000–$FFFF.
2.4 Programmable Read-Only Memory (PROM)
The MC68HC711D3 has 4-Kbytes of one-time programmable read-only memory (OTPROM). The PROM
address is $F000–$FFFF in all modes except expanded multiplexed. In expanded- multiplexed mode, the
PROM is located at $7000–$7FFF after reset.
The on-chip read-only memory (ROM) of an MC68HC711D3 is programmed in MCU mode. In this mode,
the PROM is programmed through the MCU in the bootstrap or test modes. The erased state of a PROM
byte is $FF.
Using the on-chip OTPROM programming feature requires an external 12-volt nominal power supply
(V_PP). Normal programming is accomplished using the OTPROM programming register (PPROG).
As described in the following subsections, these two methods of programming and verifying EPROM are
possible:
1. Programming an individual EPROM address
2. Programming the EPROM with downloaded data
2.4.1 Programming an Individual EPROM Address
In this method, the MCU programs its own EPROM by controlling the PPROG register. Use these
procedures to program the EPROM through the MCU with:
• The ROMON bit set in the CONFIG register
• The 12-volt nominal programming voltage present on the XIRQ/V_PP pin
• The IRQ pin must be pulled high.
EPROG
LDAB
STAB
STAA
LDAB
STAB
JSR
CLR
#$20
$003B
$0,X
#$21
$003B
DLYEP
$003B
Set ELAT bit (PGM = 0) to enable
EPROM latches.
Store data to EPROM address
Set PGM bit with ELAT = 1 to enable
EPROM programming voltage
Delay 2–4 ms
Turn off programming voltage and set
to READ mode
MC68HC711D3 Data Sheet, Rev. 2.1
Freescale Semiconductor
31