HC05 datasheet(191/232 Pages) MOTOROLA

191 / 232 page

MC68HC05X16

Rev. 1

MOTOROLA

B-7

MC68HC705X32

B.5

EPROM

The MC68HC705X32 memory map is given in Figure B-2. The device has a total of 31248 bytes

of EPROM. 16 bytes are used for the reset and interrupt vectors from address $7FF0 to $7FFF.

The main EPROM block of 31232 bytes is located from $0400 to $7DFF. One byte of EPROM is

used as an option register and is located at address $7FDE.

The EPROM can be completely tested before assembly with sequences of both program and

erase. It is ﬁnally erased before being typically assembled in a package with no erase window.

Therefore, only programming is possible and the EPROM operates as a PROM.

The EPROM array is supplied by the VPP6 pin in both read and program modes. Typically the

user’s software would be loaded into a programming board where VPP6 is controlled by one of the

bootstrap loader routines. It would then be placed in an application where no programming occurs.

In this case the VPP6 pin should be hardwired to VDD.

Warning: A minimum VPP6R voltage must be applied to the VPP6 pin at all times, including

power-on. Failure to do so could result in permanent damage to the device. Unless

otherwise stated, EPROM programming is guaranteed at ambient temperature (25

°C)

only.

B.5.1

EPROM read operation

The execution of a program in the EPROM address range or a load from the EPROM are both read

operations. The E6LAT bit in the EPROM/EEPROM control register should be cleared to ‘0’ which

automatically resets the E6PGM bit. In this way the EPROM is read like a normal ROM. Reading

the EPROM with the E6LAT bit set will give data that does not correspond to the actual memory

content. As interrupt vectors are in EPROM, they will not be loaded when E6LAT is set. Similarly,

the bootstrap ROM routines cannot be executed when E6LAT is set. In read mode, the VPP6 pin

must be at the VPP6R level. When entering the STOP mode, the EPROM is automatically set to the

read mode.

Note:

An erased byte reads as $00.

189

HC05 Datasheet(PDF) 191 Page - Motorola, Inc