Zilog Z80180 Manual do Utilizador descarregar pdf (Página 153)

Z8018x

Family MPU User Manual

138

UM005003-0703

Modem Control Signals

ASCI channel 0 has CTS0

, DCD0 and RTS0 external modem control

signals. ASCI channel 1 has a CTS1

modem control signal which is

multiplexed with Clocked Serial Receive Data (RXS).

CTS0

: Clear to Send 0 (Input)

The CTS0

input allows external control (start/stop) of ASCI channel 0

transmit operations. When CTS0

is High, the channel 0 TDRE bit is held

0 whether or not the TDR0 (Transmit Data Register) is full or empty.

When CTS0

is Low, TDRE reflects the state of TDR0. The actual

transmit operation is not disabled by CT High, only TDRE is inhibited:

DCD0

: Data Carrier Detect 0 (Input)

The DCD

0 input allows external control (start/stop) of ASCI channel 0

receive operations. When DCD0 is High, the channel 0 RDRF bit is held

at 0 whether or not the RDR0, (Receive Data Register) is full or empty.

ASCI1 Time Constant Low Register (I/O Address: 1CH) (Z8S180/L180-Class Processors

Only)

Bit 76543210

R/W R/W R/W R/W R/W R/W R/W R/W R/W

Reset 0 00 00 00 0

Note: R = Read W = Write X = Indeterminate ? = Not Applicable

ASCI1 Time Constant High Register (I/O Address: 1DH) (Z8S180/L180-Class Processors

Only)

Bit 76543210

R/W R/W R/W R/W R/W R/W R/W R/W R/W

Reset 0 00 00 00 0

Note: R = Read W = Write X = Indeterminate ? = Not Applicable

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