MC68332ACEH25 Datasheet, PDF (34/88 Pages) Freescale Semiconductor, Inc – Technical Summary 32-Bit Modular Microcontroller

Freescale Semiconductor, Inc.
CSORBT —Chip-Select Option Register Boot ROM
$YFFA4A
15
14
13
12
11
10
9
6
5
4
3
1
0
MODE
BYTE
R/W
STRB
DSACK
SPACE
IPL
AVEC
RESET:
0
1
1
1
1
0
1
1
0
1
1
1
0
0
0
0
CSOR[10:0] —Chip-Select Option Registers
$YFFA4E–$YFFA76
15
14
13
12
11
10
9
6
5
4
3
1
0
MODE
BYTE
R/W
STRB
DSACK
SPACE
IPL
AVEC
RESET:
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
CSORBT, the option register for CSBOOT, contains special reset values that support bootstrap opera-
tions from peripheral memory devices.
The following bit descriptions apply to both CSORBT and CSOR[10:0] option registers.
MODE — Asynchronous/Synchronous Mode
0 = Asynchronous mode selected (chip-select assertion determined by internal or external bus con-
trol signals)
1 = Synchronous mode selected (chip-select assertion synchronized with ECLK signal)
In asynchronous mode, the chip select is asserted synchronized with AS or DS.
The DSACK field is not used in synchronous mode because a bus cycle is only performed as a syn-
chronous operation. When a match condition occurs on a chip select programmed for synchronous op-
eration, the chip select signals the EBI that an ECLK cycle is pending.
BYTE — Upper/Lower Byte Option
This field is used only when the chip-select 16-bit port option is selected in the pin assignment register.
The following table lists upper/lower byte options.
Byte
00
01
10
11
Description
Disable
Lower Byte
Upper Byte
Both Bytes
R/W — Read/Write
This field causes a chip select to be asserted only for a read, only for a write, or for both read and write.
Refer to the following table for options available.
R/W
Description
00
Reserved
01
Read Only
10
Write Only
11
Read/Write
STRB — Address Strobe/Data Strobe
0 = Address strobe
1 = Data strobe
This bit controls the timing for assertion of a chip select in asynchronous mode. Selecting address
strobe causes chip select to be asserted synchronized with address strobe. Selecting data strobe caus-
es chip select to be asserted synchronized with data strobe.
MOTOROLA
34
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MC68332
MC68332TS/D