Datasheet

Chip-Select Registers
MC68HC812A4 Data Sheet, Rev. 7
Freescale Semiconductor 89
8.6 Chip-Select Registers
This section describes the chip-select registers.
8.6.1 Chip-Select Control Register 0
Read: Anytime
Write: Anytime
Bits have no effect on the associated pin in single-chip modes.
CSP1E — Chip-Select Program 1 Enable Bit
This bit effectively selects the holes in the memory map. It can be used in conjunction with CSP0 to
select between two 2-Mbyte devices based on address ADDR21.
1 = Enables this chip-select which covers the space $8000 to $FFFF or full map $0000 to $FFFF
0 = Disables this chip-select
CSP0E — Chip-Select Program 0 Enable Bit
1 = Enables this chip-select which covers the program space $8000 to $FFFF
0 = Disables this chip-select
CSDE — Chip-Select Data Enable Bit
1 = Enables this chip-select which covers either $0000 to $7FFF (CSDHF = 1) or $7000 to $7FFF
(CSDHF = 0)
0 = Disables this chip-select
CS3E — Chip-Select 3 Enable Bit
1 = Enables this chip-select which covers a 128-byte space following the register space
($x280–$x2FF or $xA80–$xAFF) Alternately, it can be active for accesses within the extra page
window.
0 = Disables this chip-select
CS2E — Chip-Select 2 Enable Bit
1 = Enables this chip-select which covers a 128-byte space following the register space
($x380–$x3FF or $xB80–$xBFF)
0 = Disables this chip-select
CS1E — Chip-Select 1 Enable Bit
CS2 and CS3 have a higher precedence and can override CS1 for a portion of this space.
1 = Enables this chip-select which covers a 256-byte space following the register space
($x300–$x3FF or $xB00–$xBFF)
0 = Disables this chip-select
Address: $003C
Bit 7654321Bit 0
Read: 0
CSP1E CSP0E CSDE CS3E CS2E CS1E CS0E
Write:
Reset:00100000
= Unimplemented
Figure 8-16. Chip-Select Control Register 0 (CSCTL0)