Miscellaneous
Pin 1 (VPP) is the programming voltage input pin (+12.75V needed) used to re-program the device when placed in a
special programmer. This pin is always tied to the +5V standby supply, to ensure that the device can never be
re-programmed inside the television chassis.
Pin 30 is not used in this device. However, it is still connected to the MMU1 line from the m icrocontroller for use with larger
size MTP?s/EPROM?s. This line can be used to access a further 256Kbytes if such a device was fitted.
Pin 31 is the active-low programming enable pin that is used to re-program and erase the device. This pin is always
connected to the +5V standby supply to ensure that no inadvertent writes/erases are performed on the device.
SRAM (I003)
On future chassis, the position I003 will be used to hold an SRAM for teletext page storage and memory storage. A
128Kbyte device will most likely be situated here to allow 100 teletext pages to be acquired and stored for immediate fast
access to them. The SRAM is connected to the microcontroller?s address and data lines, which are shared with the
EPROM/MTP in position I002.
Supply/Ground Connections
Pins 32 and 16 are the +5V supply and ground connections respectively. This device always has +5V connected to it, even
when the TV is in the standby state.
Address Line Connections
Pins 2 to 12, 23, 31 and 25 to 28 are the address lines needed to access the 128Kbyte of data by the microcontroller.
Data Line Connections
Pins 13 to 15 and 17 to 21 are the 8-bit data lines needed to receive/transmit a byte of data at a time to/from the
microcontroller.
Chip Enable Connections
Pins 22 and 30 are 2 chip enable inputs that need to be LOW and HIGH respectively for the 128Kbyte device to operate. If
either pin 22 is HIGH or pin 30 is LOW, then the device enters a standby state whereby its power consumption is
dramatically reduced (10uW). The MMU3 output pin from the microcontroller (pin 2) is used to select the SRAM when it is
HIGH. If this pin is low, then the MTP/EPROM in position I002 is selected instead.
Write Enable Connections
Pin 29 is the active-low write enable input used to enable data to be stored inside the device. This pin is connected to the
read/write line of the microcontroller for synchronisation purposes.
74HC04 Hex Inverter (I004)
The 14-pin IC in position I004 is a high speed CMOS hex inverter used to invert digital signals. The package consists of 6
inverters, but only 4 are used in this application. |
ACEC
HITACHI
