
PSB 7280
Semiconductor Group
93
Data Sheet 1998-07-01
Chip Version Number Register
Read
Address 2000
H
Value after reset: 20
H
External Memory Interface Register
Read/Write
Address 2001
H
Value after reset: 00
H
VN(5-0)
Version Number of Chip
LDMEM
Load Memory. If LDMEM = 0, the external memory interface is
connected with the program bus. It is used for connecting an external
software RAM or EPROM.
If LDMEM = 1, the external memory interface address and data buses
are connected to the outputs of registers address low/high (at host
address 44/45
H
) and data low/high (at host address 46/47
H
),
respectively. This mode is used to download a program into an external
RAM.
If EA=1 and LDMEM = 0: Enable address lines (CA bus) to external
SRAM for program/data fetch; no meaning in other cases.
0: CA bus switched off, no program/data fetch possible (reset value).
1: CA bus active, external program/data fetch possible.
Data Access, selects program or data memory connected to
SRAM-interface.
0: program memory connected (reset value).
1: data memory connected, can be written by using “MOV” instruction,
must be read by using “MOVP”.
Number of wait states for external interface. The number of wait states
is NRW (1111
B
= 0 wait states, 0000
B
= 15 wait states), takes the value
0000
B
after reset. SRAM connected for development purpose should be
capable of zero wait states.
CAEN
DACC
NRW(3-0)