Hardware manual

Rev. 3.0, 09/98, page 56 of 361
3.3 Mode Control Register (MDCR)H'FFC5
Bit:76543210
MDS1 MDS0
Initial value:111001**
Read/Write: R R R R R R R R
Note: Initialized according to MD
1
and MD
0
inputs.
The mode control register (MDCR) is an eight-bit register that indicates the operating mode of the
chip.
Bits 7 to 5Reserved:
These bits cannot be modified and are always read as “1.”
Bits 4 and 3Reserved:
These bits cannot be modified and are always read as “0.”
Bit 2Reserved:
This bit cannot be modified and is always read as “1.”
Bits 1 and 0Mode Select 1 and 0 (MDS1 and MDS0):
These bits indicate the values of the
mode pins (MD
1
and MD
0
), thereby indicating the current operating mode of the chip. MDS1
corresponds to MD
1
and MDS0 to MD
0
. These bits can be read but not written. When the mode
control register is read, the levels at the mode pins (MD
1
and MD
0
) are latched in these bits.