Siemens EF 88H Series Manual de usuario descargar pdf (Pagina 23)

Semiconductor Group 3 - 15

Memory Organization

3.4.2 Control of XRAM in the SAB 80C517A

There are two control bits in register SYSCON which control the use and the bus operation during

accesses to the additional On-Chip RAM in XDATA range ( XRAM).

Special Function Register SYSCON

Reset value of SYSCON is XXXX XX01B.

The control bit XMAP0 is a global enable/disable bit for the additional On-Chip RAM (XRAM). If this

bit is set, the XRAM is disabled, all MOVX accesses use external memory via the external bus. In

this case the SAB80C517A can’t use the additional On-Chip RAM and is compatible with the types

without XRAM.

Bit Function

XMAP0 Global enable/disable bit for XRAM memory.

XMAP0 = 0: The access to XRAM (= On-Chip XDATA memory) is enabled.

XMAP0 = 1: The access to XRAM is disabled. All MOVX accesses are performed by

the external bus.

XMAP1 Control bit for RD

/WR signals during accesses to XRAM; this bit has no effect if

XRAM is disabled (XMAP0 = 1) or if addresses outside the XRAM address range are

used for MOVX accesses.

XMAP1 = 0: The signals RD

and WR are not activated during accesses to XRAM.

XMAP1 = 1: The signals RD

and WR are activated during accesses to XRAM.

76543210

MSB LSB

Bit No.

SYSCONAddr. 0B1

––––––

XMAP1 XMAP0

1 2 ... 18 19 20 21 22 23 24 25 26 27 28 ... 136 137

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Siemens EF 88H Series Manual de usuario Pagina 23