SPMC68CK338CPV14 datasheet(30/133 Pages) FREESCALE

30 / 133 page

MOTOROLA

MC68CK338

MC68CK338TS/D

3.6 Chip-Selects

Typical microcontrollers require additional hardware to provide external chip-select and address de-

code signals. The MC68338 includes 12 programmable chip-selects that can provide 2 to 16-clock-cy-

cle access to external memory and peripherals. Address block sizes of two Kbytes to one Mbyte can be

selected. Figure 11 is a functional diagram of a chip-select circuit.

Chip-select assertion can be synchronized with bus control signals to provide output enable, read/write

strobe, or interrupt acknowledge signals. Chip-select logic can also generate DSACK and AVEC signals

internally. Each signal can also be synchronized with the ECLK signal available on ADDR23.

Figure 11 Chip-Select Circuit Block Diagram

NOTES:

1. All transfers are aligned. The CPU32L does not support misaligned word or long-word transfers.

2. Operands in parentheses are ignored by the CPU32L during read cycles.

3. 3-Byte transfer cases occur only as a result of a long word to 8-bit port transfer.

Table 16 Operand Alignment

Current

Cycle

Transfer Case1

SIZ1

SIZ0

ADDR0

DSACK1 DSACK0

DATA

[15:8]

DATA

[7:0]

Cycle

Byte to 8-bit port (even)

OP0

(OP0)2

—

Byte to 8-bit port (odd)

OP0

(OP0)

—

Byte to 16-bit port (even)

OP0

(OP0)

—

Byte to 16-bit port (odd)

(OP0)

OP0

—

Word to 8-bit port

OP0

(OP1)

Word to 16-bit port

OP0

OP1

—

3-byte to 8-bit port3

OP0

(OP0)

Long word to 8-bit port

OP0

(OP0)

Long word to 16-bit port

OP0

OP1

CHIP SEL BLOCK

AVEC

GENERATOR

DSACK

GENERATOR

ASSIGNMENT

DATA

BASE ADDRESS REGISTER

TIMING

AND

CONTROL

ADDRESS COMPARATOR

OPTION COMPARE

OPTION REGISTER

AVEC

DSACK

BUS CONTROL

INTERNAL

SIGNALS

ADDRESS

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

SPMC68CK338CPV14 Datasheet(PDF) 30 Page - Freescale Semiconductor, Inc

SPMC68CK338CPV14 Datasheet(HTML) 30 Page - Freescale Semiconductor, Inc

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL