mc68hc705j2 Freescale Semiconductor, Inc, mc68hc705j2 Datasheet - Page 56

• Manufacturer Part Number: mc68hc705j2
• Description: 8-bit Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

6.1.3 EPROM
6.1.3.1 EPROM Programming
PROG — EPROM Programming Register
RESET
LATCH — EPROM Bus Latch
EPGM — EPROM Programming
Bits 7–3 and 1 — Not used; always read as zeros.
MOTOROLA
6-4
This read/write bit causes address and data buses to be latched for EPROM
programming. Clearing the LATCH bit automatically clears the EPGM bit.
This read/write bit applies programming power to the EPROM. To write the EPGM
bit, the LATCH bit must already be set.
Two Kbytes of user EPROM for storage of program instructions and fixed data
are located at addresses $0700–$0EFF. The eight addresses from $0FF8–
$0FFF are EPROM locations reserved for interrupt vectors and reset vectors.
Eight additional EPROM bytes are located at $0FF0–$0FF8. There are two
ways to write data to the EPROM:
The EPROM programming register, shown in Figure 6-3, contains the control
bits for programming the EPROM.
1 = Address and data buses configured for EPROM programming
0 = Address and data buses configured for normal operation
1 = EPROM programming power switched on
0 = EPROM programming power switched off
• The EPROM programming register contains the control bits for
• The bootloader ROM contains routines to download the contents of an
Bit 7
0
0
programming the EPROM on a byte-by-byte basis.
external memory device to the on-chip EPROM.
Figure 6-3. EPROM Programming Register (PROG)
6
0
0
5
0
0
M E M O R Y
4
0
0
3
0
0
LATCH
2
0
1
0
0
MC68HC705J2
EPGM
Bit 0
0
$ 0 0 1 C