ST92195C STMicroelectronics, ST92195C Datasheet - Page 91

• Manufacturer Part Number: ST92195C
• Description: 48-96 Kbyte Rom Hcmos Mcu With On-screen Display And Teletext Data Slicer
• Manufacturer: STMicroelectronics

ST92195C/D - TELETEXT DISPLAY STORAGE RAM INTERFACE
TDSRAM (Cont’d)
7.3.4 Register Description
7.3.4.1 Data Registers
BUF0..15 R240 .. R255 Page 36Read/Write
RAM Buffer Data Register x = 0,..,15
BUF16..31 R240 .. R255 Page 37 Read/Write
RAM Buffer Data Register x = 16,..,31
BUF32..39 R240 .. R247Page 38 Read/Write
RAM Buffer Data Register x = 32,..,39
Reset Value: xxxx xxxx (xxh)
Bits 7:0 = BUFx[7:0]: presents the x-th byte
(MSB...LSB) of the 40 byte data buffer belonging
to the teletext function. The data registers are not
accessible during the transfer (BUSY = “1”). A
buffer exchange starts with BUF0 and ends with
BUF39 whether the address is incremented or
decremented.
7.3.4.2 Address Registers
MULTI-BYTE TRANSFER START ADDRESS
REGISTER 1 (MBTSA1)
R250 - Read/Write
Register Page: 38
Reset Value: 1000 0000 (80h)
Bits 7:6 = Hard wired to map correctly into the
memory space, defined for the RAM.
Bit 5 = SA[13]: This bit must always be written to
0.
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BUFx.7 BUFx.6 BUFx.5 BUFx.4 BUFx.3 BUFx.2 BUFx.1 BUFx.0
7
7
1
0
SA13 SA12 SA11 SA10
SA9
SA8
0
0
Bits 4:0 = SA[12:8]: Bit13..bit8 of the 13-bit start
address for the 40-byte data transfer have to be
written into this register.
MULTI-BYTE TRANSFER START ADDRESS
REGISTER 0 (MBTSA0)
R251 - Read/Write
Register Page: 38
Reset Value: 0000 0000 (00h)
Bits 7:0 = SA[7:0]: Bit7..bit0 of the 13-bit start ad-
dress for the 40-byte data transfer have to be writ-
ten into this register.
MBTSA1..MBTSA0 are not accessible during the
transfer (BUSY = ”1”).
MBTSA is used as a counter to generate the TD-
SRAM (R/W) address. When the Multi-Byte Trans-
fer is done, this register is incremented or decre-
mented by 40 depending on the BADU bit in the
BUFC register R248 page 26h.
The normal mode corresponds to a counter incre-
mentation.
When the user wants to use decrementation mode
(using the BADU bit), the address must be com-
plemented before writing to the 13 LSB of
MBTSA1.. MBTSA0.
For example, to decrement the counter from the
address:
– SA12 SA11........ SA0 = 1 0101 0101 0101b =
the software must load:
– SA12n SA11n........ SA0n = 0 1010 1010 1010b
in the start address register. The BADU bit must
be set to 1.
The value read in this case will be MBTSA1..
MBTSA0 = 8AAAh (The 3 MSB are hard wired).
SA7
1555h,
= 0AAAh,
7
SA6
SA5
SA4
SA3
SA2
SA1
SA0
0