AS2578BN AMSCO [austriamicrosystems AG], AS2578BN Datasheet - Page 5

• Manufacturer Part Number: AS2578BN
• Description: TELEPHONE CONTROLLER WITH 13 MEMORIES AND 2-WIRE BUS
• Manufacturer: AMSCO [austriamicrosystems AG]

Data Sheet
After a recall a pause will automatically be generated.
The pause time is 3 sec.
The ground loop (GL) has two pulse lengths, namely a
short of 500 ms and a long of 1250 ms.
Short GL: If the recall key is depressed for 540 ms, the
GL pulse is 500 ms.
Long GL: If the recall key is depressed for > 540 ms, the
GL pulse is 1250 ms.
During redial a ground loop is only executed as a long GL
(1250 ms).
Automatic pauses are generated in the following manner:
- always after a recall independent of the AP pin
- with automatic pause insertion enabled by pin option
A pause read from the RAM can be terminated (shortened)
prior to time out by a low level on AP pin (AS2578 only)
during the pause execution. The pause time is 3 sec.
During execution of a pause, mute is inactive, i.e. the
circuit is in speech mode.
Sliding Cursor Procedure (AS2578 only)
To accommodate redialling (LNR) behind a PABX without
using automatic pause generation, a sliding cursor
protocol is implemented. The sliding cursor is enabled
when AP = high. If new entries match the previous RAM
contents, pressing the LNR key will dial out the remaining
digits.
If there is an error in matching, the LNR will be inhibited
until next on-hook, and the RAM will contain the new
number.
Serial Interface
The AS2578 /B support a bidirectional bus oriented
Rev. 3
Pause Generation
Pause introduces a delay in signalling digit strings to
accommodate second and subsequent dial tones.
or LM code, up to two pauses can be automatically
inserted at any location of the original entry in the RAM
(except location 1 of the digit string), when the mute
output goes inactive (in MF mode for more than 1 sec.)
before next entry.
5
protocol. The protocol defines any device that sends
data onto the bus as a transmitter, and the receiving
device as the receiver. The AS2578 /B are controlling the
transfer and hence the master. The EEPROM being
controlled is the slave.
The AS2578 /B will always initiate data transfer, and
provide the clock for both transmit and receive operations.
Therefore, the protocol is for single master applications
only.
However, a temporary second master can be used to
write into the EEPROM when the AS2578 /B are supplied
and in idle state.
Clock and Data Conventions
Data states on the SDA line can change only during SCL
low. SDA state changes during SCL high are reserved
for indicating start and stop conditions (see figure 1 and
2).
Start Condition
All commands are preceded by the start condition, which
is a high to low transition of SDA when SCL is high. The
slave should continuously monitor the SDA and SCL
lines for the start condition and must not respond to any
command until this condition has been met.
Stop Condition
All communications are terminated by a stop condition,
which is low to high transition of SDA when SCL is high.
The stop condition is also used to place the slave in the
standby power mode.
Acknowledge
Acknowledge is a software convention used to indicate
successful data transfers. The transmitting device, either
master or slave, will release the bus after transmitting
eight bits. During the ninth clock cycle the receiver will
pull the SDA line low to acknowledge that it received the
eight bits of data (see figure 3).
The slave should always respond with an acknowledge
after recognition of a start condition and its slave address.
If both the device and a write operation have been
selected, the slave should respond with an acknowledge
after receipt of each subsequent eight bit word.
In the read mode, when the EEPROM has transmitted
eight bits of data, it should release the SDA line and
monitor the line for an acknowledge. If the AS2578 /B
respond with an acknowledge and does not generate a
stop condition, the EEPROM should continue to transmit
data. If the AS2578 /B do not respond with an
acknowledge, the EEPROM should terminate further
AS2578 /B
March 1997