6-8 MC68VZ328 User’s Manual
Programming Model
6.3.3 Chip-Select Registers

There are four 16-bit chip-select (CSA, CSB, CSC, and CSD) registers for each corresponding chip-select

base address register. Each register controls two chip-select signals and can be configured to select the

memory type and size of the memory range supported as well as to program the re qui re d wai t s ta te s or us e

the external DTACK signal. The settings for the registers are described in Table6-7 through Table 6-10 on

page 6-14.

CSA Chip-Select Register A 0x(FF)FFF110

BIT
15 14 13 12 11 10 9 8 7 654321
BIT
0
RO FLASH BSW WS3–1 SIZ EN
TYPE rw rw r w rw rw rw rw rw rw w
RESET 0 0 0 0 0 0 0 0 1 011000 0
0x00B0
Table 6-7. Chip-Select Register A Description
Name Description Setting
RO
Bit 15 Read-Only—This bit sets the chip-select to
read-only. Otherwise, read and write accesses
are allowed. A write to a read-only area will
generate a bus error if the BETEN bit of the
SCR is set. See Section5.2.1, “System Control
Register,” on page5-2 for more information.
0 = Read/write.
1 = Read-only.
Reserved
Bits 14–9 Reserved These bits are reserved and should be set to 0.
FLASH
Bit 8 Flash Memory Support—When enabled, this
bit provides support for flash memory by fo rc-
ing the LWE/UWE signal to go active after
chip-select.
Note: This bit is used for expanded memory
size for CSD when the DRAM bit in the CSD
register is enabled.
0 = The chip-select and LWE/UWE si gnals go activ e
at the same clock edge.
1 = The chip-select signal goes low 1 clock before
LWE/UWE.
BSW
Bit 7 Data Bus Width—This bit sets the data bus
width for this chip-select area. 0 = 8 bit.
1 = 16 bit.
WS3–1
Bits 6–4 Wait State—This field determines the number
of wait states added before an internal DTACK
signal is returned for this chip-select.
Note: When using the external DTACK
signal, you must configure the
BUSW/DTACK/PG0 pin.
000 = 0 + WS0 wait states.
001 = 2 + WS0 wait states.
010 = 4 + WS0 wait states.
011 = 6 + WS0 wait states.
100 = 8 + WS0 wait states.
101 = 10 + WS0 wait states.
110 = 12 + WS0 wait states.
111 = External DTACK.
When using the external DTACK signal, you must
select DTACK function in Port G.
WS0 is the DWS0, CWS0, BWS0, or AWS0 bit in
the CSCTRL1 register.