COP8SE National Semiconductor, COP8SE Datasheet - Page 12

• Manufacturer Part Number: COP8SE
• Description: 8-Bit CMOS ROM Based and OTP Microcontrollers with 4k Memory and 128 Bytes EERAM
• Manufacturer: National Semiconductor

www.national.com
5.0 Functional Description
Caution: In order to prevent the unexpected setting of the ILRW of the
1. The Segment Register (S) = 01,
2. The B Register points to the EERAM, i.e. B 7F (hex),
3. One of the following instructions is executed: SC, RC, IFC, IFNC, NOP,
3a. if any instruction is skipped.
Warning: The segment register should not point to the EE-
RAM unless the EERAM is addressed. This will prevent in-
advertent writes to EERAM.
5.4.1. E2CFG and EE Support Circuitry
The EERAM module contains EERAM support circuits to
generate all necessary high voltage programming pulses.
The E2CFG register provides control and status functions for
the EERAM module. The E2CFG register bit assignments
are shown below. The E2CFG register is set to 0 on RESET
except the E2BUSY bit, which is unaffected. The EECFG
register can be accessed at any time without error.
5.5 DATA MEMORY SEGMENT RAM EXTENSION
Data memory address 0FF is used as a memory mapped lo-
cation for the Data Segment Address Register (S).
R/W
Bit 7
RESERVED These bits are reserved and must be 0.
E2PEND
E2ILRW
E2BUSY
E2EI
and
and
RPND, SWAPA, JMPL, VIS or LD B, Imm with Imm 7F (hex),
or
Reserved, must be 0
R/W
E2CFG Register and the corresponding interrupt, the use of the X
Register and direct addressing are recommanded for EERAM ac-
cess. It is further recommended that the B Register be set to a
value between 80 (hex) and FF (hex) before setting the Segment
register to 1 and that this value be retained until S is set back to 0.
Due to an artifact of the COP8 architecture, the ILRW bit of the
E2CFG Register will be set and an interrupt will be generated un-
der the following conditions:
R/W
Interrupt Pending Bit. This bit indicates that
a write operation has completed and a Write
Complete Interrupt is pending. This bit is
logically ANDed with the E2EI bit to cause
an interrupt. This bit can be written by either
hardware or software. This bit must be reset
by software after processing the interrupt.
EERAM illegal read/write operation. This bit
is set when the EERAM array is accessed
while E2BUSY is set. This bit will cause an
EERAM
E2PEND bit, if the E2EI bit is set. This bit
can be written by either hardware or soft-
ware. This bit must be reset by software af-
ter processing the interrupt.
This bit is set by the hardware when a write
to the EERAM is in process and reset by the
hardware when the write completes. The
E2PEND bit is set when this bit is reset.
This bit is software read-only.
Interrupt Enable Bit. Setting this bit enables
EERAM interrupts. The default condition is
interrupts disabled after RESET. This bit
must be used in conjunction with the GIE
bit. This bit can be written by software only.
R/W
E2PEND
interrupt,
R/W
E2ILRW
R/W
without
E2BUSY
(Continued)
RO
setting
E2EI
R/W
Bit 0
the
12
The data store memory is either addressed directly by a
single byte address within the instruction, or indirectly rela-
tive to the reference of the B, X, or SP pointers (each con-
tains a single-byte address). This single-byte address allows
an addressing range of 256 locations from 00 to FF hex. The
upper bit of this single-byte address divides the data store
memory into two separate sections as outlined previously.
With the exception of the RAM register memory from ad-
dress locations 00F0 to 00FF, all RAM memory is memory
mapped with the upper bit of the single-byte address being
equal to zero. This allows the upper bit of the single-byte ad-
dress to determine whether or not the base address range
(from 0000 to 00FF) is extended. If this upper bit equals one
(representing address range 0080 to 00FF), then address
extension does not take place. Alternatively, if this upper bit
equals zero, then the data segment extension register S is
used to extend the base address range (from 0000 to 007F)
from XX00 to XX7F, where XX represents the 8 bits from the
S register. Thus the 128-byte data segment extensions are
located from addresses 0100 to 017F for data segment 1,
0200 to 027F for data segment 2, etc., up to FF00 to FF7F
for data segment 255. The base address range from 0000 to
007F represents data segment 0.
Figure 8 illustrates how the S register data memory exten-
sion is used in extending the lower half of the base address
range (00 to 7F hex) into 256 data segments of 128 bytes
each, with a total addressing range of 32 kbytes from XX00
to XX7F. This organization allows a total of 256 data seg-
ments of 128 bytes each with an additional upper base seg-
ment of 128 bytes. Furthermore, all addressing modes are
available for all data segments. The S register must be
changed under program control to move from one data seg-
ment (128 bytes) to another. However, the upper base seg-
ment (containing the 16 memory registers, I/O registers,
control registers, etc.) is always available regardless of the
contents of the S register, since the upper base segment
(address range 0080 to 00FF) is independent of data seg-
ment extension.
The instructions that utilize the stack pointer (SP) always ref-
erence the stack as part of the base segment (Segment 0),
regardless of the contents of the S register. The S register is
FIGURE 8. RAM Organization
DS100973-45