Epson S1C05251 Technical Manual page 14

3 FUNCTIONAL DESCRIPTION
Each register is detailed below.
MDR: Mode Register (Address = 0h)
Bit Bit name
D0 SYNC
D1 BT
D2 SEL
D3 TEST
8
Table 3.1.2 MDR register
Initial
value
0 Asynchronous/synchronous mode selection
This bit is used to select asynchronous or synchronous mode.
SYNC bit
0 Selects asynchronous mode
1 Selects synchronous mode
Asynchronous mode is selected by setting this bit to 0, in which case the 8-bit
serial data output from the SDO pin is forwarded in asynchronous mode.
Synchronous mode is selected by setting this bit to 1. When the FSK signal is
received in FSK mode, serial data is output from the SDO pin and read by the
CPU synchronously with the clock signal fed from the CPU to the #SCLK pin.
Also, in synchronous mode, when the receive data is ready for output, the #IRQ
pin changes to Low level, indicating that the CPU can read the data.
0 Bellcore/BT selection
This bit is used to select Bellcore or BT (British Telecom) mode.
BT bit
0
1
When this bit is set to 0, the gain in the dual-tone filter is set directly by the GLR
and GHR registers.
When this bit is set to 1, the value set by the GLR (Table 3.1.3) and GHR (Table
3.1.4) registers plus 6 dB is set as the gain in the dual-tone filter.
0 FSK/CPM mode selection
This bit is used to select FSK or CPM mode when the MODE0 pin is low.
SEL bit
0
1
If this bit is set to 1 when the MODE0 pin is held at Low level (FSK/CPM mode),
the receive filter is bypassed, and when the CPM tone is input to the INP/INN pin,
the #IRQ pin goes to Low level. Also, since the pulse generated from the CPM
tone signal is output from the #DET pin, the CPM (dial) tone can be identified by
measuring the frequency of the pulse.
If this bit is set to 0 when the MODE0 pin is held at Low level (FSK/CPM mode),
the FSK function is enabled.
If this bit is set to 1 when the MODE0 pin is high (CAS mode), the CAS signal can
be input to the CASIN pin. If this bit is set to 0 when the MODE0 pin is high, the
CAS signal can be input to the INP/INN pin.
0 Test mode selection
This bit is used to test the IC. This bit normally must be fixed to 0.
Description
Mode
Mode
Selects Bellcore mode
Selects BT mode
Mode
Selects FSK mode
Selects CPM mode
EPSON
S1C05251 TECHNICAL MANUAL