MC68HC05L28 Datasheet, PDF (41/156 Pages) Motorola, Inc – Flexible general-purpose microcomputer

3.4.2.1 ELAT — EPROM latch control
1 (set) – When this bit is set to 1, the EPROM address and data buses are
configured for programming. This causes the address and data
buses to be latched when a write to EPROM is executed. The
EPROM cannot be read if it is set to 1.
3
0 (clear) – The EPROM address and data buses are configured for normal
reads.
3.4.2.2 PGM — EPROM program control
1 (set)
– Programming power is connected to the EPROM array.The PGM can
only be set if ELAT is set and it is automatically cleared when ELAT =
0.
0 (clear) – EPROM address and data bus are configured for normal reads.
Note: ELAT and PGM cannot be set in the same write operation.
Take the following steps to program a byte of EPROM:
– Apply the programming voltage V_PP to the VPP pin.
– Set the ELAT bit.
– Write to the EPROM address.
– Set the PGM bit for a time t_PROG to apply the programming voltage.
– Clear the ELAT and PGM bits.
Note: The erased state of the EPROM is $00.
MC68HC05L28
MEMORY AND REGISTERS
TPG
MOTOROLA
3-5