PC87782 datasheet(12/17 Pages) NSC

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Memory Map

The CompactRISC architecture supports a uniform linear ad-

dress space of 256K bytes. The PC87782 implementation of

this architecture uses only the lowest 128K bytes of address

space, ranging from 00000 to 1FFFF hex. The remaining

128K bytes (20000 to 3FFFF hex) are not used by the device.

Table 7 is a memory map showing the types of memory and

peripherals that occupy this memory space. Address ranges

not listed in the table are reserved and should not be read or

written.

Table 8 is a detailed memory map showing the speciﬁc mem-

ory address of the memory, I/O ports, and registers. The ta-

ble shows the starting address, the size, and a brief

description of each memory block and register. For detailed

information on using these memory locations, see the appli-

cable sections in the data sheet.

All addresses not listed in the table are reserved and should

not be read or written. An attempt to access an unlisted ad-

dress will have unpredictable results.

Each byte-wide register occupies a single address and can

be accessed only in a byte-wide transaction. Each word-wide

can be accessed only in a word-wide transaction. Both the

byte-wide and word-wide registers reside at word boundaries

(even addresses). Thus, each byte-wide register uses only

the lowest eight bits of the internal data bus.

Most PC87782 registers are read/write registers. However,

some registers are read-only or write-only, as indicated in the

table. An attempt to read a write-only register or to write a

read-only register will have unpredictable results.

When the software writes to a register in which one or more

bits are reserved, it must write a zero to each reserved bit un-

less indicated otherwise in the description of the register.

Reading a reserved bit returns an undeﬁned value.

SCL

OD-TTL

ACCESS.bus Serial Clock signal

SDA

OD-TTL

ACCESS.bus data signal

Table 6 Power Supply

Signal

Pin Number

No. of

Sig Pins

Function

100-pin

160-pin

AVCC

Analog 5V power supply.

VCC

Digital 5V power supply.

AGND

Analog ground, for A/D and D/A.

GND

Ground for on-chip logic and output drivers.

VCC

N/A

Digital 5V power supply.

GND

N/A

Ground for on-chip logic and output drivers.

Table 5 Input/Output Pins

Signal

Type

Pin Number

No. of

Sig Pins

Function

100-pin

160-pin

Table 7 PC87782 Memory Map

Address (hex) Size

Description

BIU Zone

00000

− 07FFF 32K Base Memory

Zone 0

08000

− 0DFFF 24K Reserved

0E000

− 0E1FF 512 LAN Receive Buffer

RAM

N/A

0EA90

− 0F56F 2784 System RAM

0F800

− 0F87F 128 LAN Transmit Buffer

RAM

0F900

− 0F98F

BIU Registers

0FB00

− 0FBFF 256 I/O Expansion

0FC00

− 0FFFF

On-chip module

registers

10000

− 1FFFF 64K Off-Chip Memory

Zone1

(IRD

mode

only)

20000

− 3FFFF 120K Reserved

Zones 2-3

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