MC68HC05B4 Datasheet, PDF (168/298 Pages) Motorola, Inc – High-density Complementary Metal Oxide Semiconductor (HCMOS) Microcomputer Unit

C.3
EPROM registers
C.3.1 EPROM control register
EPROM/ECLK control
Address bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
bit 0
State
on reset
$0007
EPPT ⁽¹⁾ ELAT EPGM ECLK
u?00 0uuu
(1) This bit is a copy of the EPP bit in the options register at $1EFE and therefore its state on reset will be the same as that for the
EPP bit.
Bit 7 — Factory use only
This bit is strictly for factory use only and will always read zero.
EPPT — EPROM protect test bit
This bit is a copy of the EPROM protect bit (EPP) located in the option register. When ELAT is set,
the EPPT bit can be tested by the software to check if the EPROM array is protected or not, since
the EPROM content is not available when ELAT is set.
POR or external reset modifies this bit to reflect the state of the EPP bit in the options register.
ELAT — EPROM programming latch enable bit
1 (set) – When set, this bit allows latching of the address and up to 4 data
bytes for further programming, provided EPGM is zero.
0 (clear) – When cleared, program and interrupt routines can be executed and
data can be read in the EPROM or firmware ROM.
STOP, power-on and external reset clear this bit.
EPGM — EPROM programming bit
This bit is the EPROM program enable bit. It can be set to ‘1’ to enable programming only after
ELAT is set and at least one byte is written to the EPROM. It is not possible to clear EPGM by
software, but clearing ELAT will always clear EPGM.
ECLK — External clock option bit
See Section 4.3.
14
MOTOROLA
C-6
MC68HC705B5
TPG
MC68HC05B6
Rev. 4