DS5001FP datasheet(5/26 Pages) DALLAS

5 / 26 page

DS5001FP

5 of 26

33, 35,

and A15 respectively.

71, 69,

67, 65,

61, 59,

57, 55

28, 26,

24, 23,

21, 20,

19, 18

BD7–0

Byte-Wide Data-Bus Bits 7–0. This 8-bit, bidirectional bus is combined with the

nonmultiplexed address bus (BA14–0) to access NV SRAM. Decoding is performed on

CE1

and CE2 . Read/write access is controlled by R/ W . BD7–0 connect directly to an

SRAM, and optionally to a real-time clock or other peripheral.

R/ W

Read/Write. This signal provides the write enable to the SRAMs on the byte-wide bus. It

is controlled by the memory map and partition. The blocks selected as program (ROM) are

write-protected.

CE1

Chip Enable 1. This is the primary decoded chip enable for memory access on the byte-

wide bus. It connects to the chip enable input of one SRAM. CE1 is lithium-backed. It

remains in a logic high inactive state when VCC falls below VLI.

N/A

CE1N

Non-battery-backed version of chip enable 1. This can be used with a 32kB EPROM. It

should not be used with a battery-backed chip.

233

CE2

Chip Enable 2. This chip enable is provided to access a second 32k block of memory. It

connects to the chip enable input of one SRAM. When MSEL = 0, the micro converts CE2

into A16 for a 128k x 8 SRAM. CE2 is lithium-backed and remains at a logic high when

VCC falls below VLI.

CE3

Chip Enable 3. This chip enable is provided to access a third 32k block of memory. It

connects to the chip enable input of one SRAM. When MSEL = 0, the micro converts CE3

into A15 for a 128k x 8 SRAM. CE3 is lithium-backed and remains at a logic high when

VCC falls below VLI.

N/A

CE4

Chip Enable 4. This chip enable is provided to access a fourth 32k block of memory. It

connects to the chip-enable input of one SRAM. When MSEL = 0, this signal is unused.

CE4

is lithium-backed and remains at a logic high when VCC < VLI.

N/A

PE1

Peripheral Enable 1. Accesses data memory between addresses 0000h and 3FFFh when

the PES bit is set to a logic 1. Commonly used to chip enable a byte-wide real-time clock

such as the DS1283. PE1 is lithium-backed and remains at a logic high when VCC falls

below VLI. Connect PE1 to battery-backed functions only.

3N/A

PE2

Peripheral Enable 2. Accesses data memory between addresses 4000h and 7FFFh when

the PES bit is set to a logic 1. PE2 is lithium-backed and remains at a logic high when VCC

falls below VLI. Connect PE2 to battery-backed functions only.

N/A

PE3

Peripheral Enable 3. Accesses data memory between addresses 8000h and BFFFh when

the PES bit is set to a logic 1. PE3 is not lithium-backed and can be connected to any type

of peripheral function. If connected to a battery-backed chip, it needs additional circuitry to

maintain the chip enable in an inactive state when VCC < VLI.

N/A

PE4

Peripheral Enable 4. Accesses data memory between addresses C000h and FFFFh when

the PES bit is set to a logic 1. PE4 is not lithium-backed and can be connected to any type

of peripheral function. If connected to a battery-backed chip, it needs additional circuitry to

maintain the chip enable in an inactive state when VCC < VLI.

N/A

PROG

Invokes the bootstrap loader on a falling edge. This signal should be debounced so that

only one edge is detected. If connected to ground, the micro enters bootstrap loading on

power-up. This signal is pulled up internally.

N/A

VRST

This I/O pin (open drain with internal pullup) indicates that the power supply (VCC)

has fallen below the VCCmin level and the micro is in a reset state. When this occurs, the

DS5001FP drives this pin to a logic 0. Because the micro is lithium-backed, this signal is

guaranteed even when VCC = 0V. Because it is an I/O pin, it also forces a reset if pulled

low externally. This allows multiple parts to synchronize their power-down resets.

N/A

This output goes to a logic 0 to indicate that VCC < VLI and the micro has switched to

lithium backup. Because the micro is lithium-backed, this signal is guaranteed even when

VCC = 0V. The normal application of this signal is to control lithium powered current to

isolate battery-backed functions from non-battery-backed functions.

MSEL

Memory Select. This signal controls the memory size selection. When MSEL = +5V, the

DS5001FP expects to use 32k x 8 SRAMs. When MSEL = 0V, the DS5001FP expects to

use a 128k x 8 SRAM. MSEL must be connected regardless of partition, mode, etc.

No Connect.

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