Z8018233FSC datasheet(78/109 Pages) ZILOG

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Z80182/Z8L182

ZILOG INTELLIGENT PERIPHERAL

PRELIMINARY

Zilog

DS971820600

Z80182/Z8L182 MIMIC DMA CONSIDERATIONS

For the PC Interface, the 16550 device has two modes of

operation that need to be supported by the MIMIC. In

single transfer mode, the DMA request line for the receiver

goes active whenever there is at least one character in the

RCVR FIFO. For the transmitter, the DMA request line is

active on an empty XMIT FIFO and inactive on non-empty.

In multi-transfer mode, the RCVR DMA goes active at the

trigger level and inactive on RCVR FIFO empty. The XMIT

DMA is active on non-full XMIT FIFO and inactive on a full

XMIT FIFO.

Bit 3 in the FCR controls the DMA mode for the PC

interface. If a 1 is programmed into this bit, multi-byte DMA

is enabled. A 0 in this bit (default) enables single byte

DMA.

As specified, the 16550 does not have any means of

handling the error status bits in the FIFO in this multi-

transfer mode. Such DMA transfers would require blocks

with some checksum or other error checking scheme.

For the MPU interface, the DMA is controlled by a non-

empty transmit FIFO and by a non-full receive FIFO

conditions (THRE and the DR bits in the LSR). If the delay

timers are enabled, the respective shadow bits are used

for DMA control. The effect of the DMA logic is to request

DMA service when at least one byte of data is available to

be read or written to the FIFO’s by the Z180. The Z180's

DMA channel can be programmed to trigger on edge or on

level.

EMULATION MODES

The Z80182/Z8L182 provides four modes of operation.

The modes are selected by the EV1 and EV2 pins. These

four modes allow the system development and commercial

production to be done with the same device. The four

emulation modes are shown in Table 20.

Table 20. EV2 and EV1, Emulation Mode Control

EV2

EV1

EV Description

Mode 0

Normal Mode, on-chip Z180 bus master

Mode 1

Emulation Adapter Mode

Mode 2

Emulator Probe Mode

Mode 3

RESERVED, for Test Use Only

through the emulation adapter. In Emulation Adaptor Mode

the Z182s, Z180 MPU and Z180 peripheral signals are tri-

state or physically disconnected. The Z182 continues to

provide its ESCC, MIMIC, chip select, and Port functions

and signals to the target system. The Mode 1 effects on the

Z182 are shown in Table 21. Note that INT1-2 Edge Detect

Logic cannot be used in Emulation Adaptor EV Mode 2.

Mode 0 Normal Mode

This is the normal operating mode for the Z80182/Z8L182.

Mode 1 Emulation Adapter Mode

The Emulation Adaptor Mode enables system development

for the Z182 with a readily available Z180 emulator. The

Emulator provides the Z180™ MPU and Z180 peripheral

functions to the target system, with their signals passing

Z8018233FSC Datasheet(PDF) 78 Page - Zilog, Inc.

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