Z80182 Datasheet, PDF (78/109 Pages) Zilog, Inc. – ZILOG INTELLIGENT PERIPHERAL CONTROLLER (ZIP™)

Zilog
PRELIMINARY
Z80182/Z8L182
ZILOG INTELLIGENT PERIPHERAL
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.
Mode 0
Mode 1
Mode 2
Mode 3
Table 20. EV2 and EV1, Emulation Mode Control
EV2
EV1
EV Description
0
0
0
1
1
0
1
1
Normal Mode, on-chip Z180 bus master
Emulation Adapter Mode
Emulator Probe Mode
RESERVED, for Test Use Only
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
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.
3-78
DS971820600