User manual

Page 19
Document No. 80-15151 Issue 6 HEBER LTD
of operation, for example, if only Sound Channel 1 is fitted, then by linking the LS1+ output to the
feedback pin, the same signal can drive BOTH loudspeakers. See Section 6.9, “Making Sounds”
below for a more detailed explanation of the different operational modes that are possible.
5.19 Serial I/O
P1 provides connections to RS232 Channel A, Data Receive & Transmit plus RTS/CTS.
P2 provides connections to RS232 Channel B, Data Receive & Transmit plus RTS/CTS and is in the
format specified by the BACTA standard.
Operation of the above two ports is determined by the operation of the Serial Module in the MC68340
Processor. Refer to the Serial Module Section of Motorola MC68340 User Manual for a full
explanation.
5.20 Internal I
2
C Bus
An internal I
2
C Bus is implemented using SIM40 Lines PORTA4 (SCL) and PORTA5 (SDA). This bus
allows the processor to read and write the optional Real Time Clock chip, U40, and the optional
E
2
PROM, U37. If neither of these devices is fitted, then these 2 lines are also available on the I/O
Expansion Connector P14 and are free for other uses.
5.20.1 Real Time Clock
U40 is a position that accepts a Philips PCF8583 I
2
C Real Time Clock. The standard Pluto 5 Controller
has a socket fitted in this position along with the 32.768KHz Crystal, X2. However, the PCF8583 IC is
NOT fitted as standard but is available as an optional extra or may be fitted by the user.
The I
2
C Slave Address of the RTC is as follows:
Table 13. I
2
C Slave Addresses for RTC, U40
READ:
0xA1
WRITE:
0xA0
5.20.2 E
2
PROM
U37 position is fitted with a socket that accepts an “Industry Standard” E
2
PROM, 24C04 (512 bytes) or
24C08 (1024 bytes) with pin 7, which serves a different function on devices from different
manufacturers, connected to GND. The Pluto 5 Controller Boards, as standard, do not have an
E
2
PROM fitted but they are available as an optional extra or may be fitted by the user.
We strongly recommend that, if a user supplies or fits his own devices, that only NM24C04 or
NM24C08 devices should be used (manufactured by Fairchild or National Semiconductor). Heber
cannot offer Technical Support for the use of devices from alternate manufacturers.
To avoid a clash of I
2
C addressing between the PCF8583 RTC and the 24Cnn E
2
PROM, A2 (Pin 3) of
the E
2
PROM is strapped to Vcc and A0/A1 to GND and this socket is restricted to accepting devices
no larger than the 24C08. Note, however, that there is no such size restriction on the devices that may
be connected via P13, the External I
2
C Bus Connector.
The I
2
C Slave Address of each of the 256 byte “Page Blocks” in the E
2
PROM, U37, is as follows:
Table 14. I
2
C Slave Addresses for E
2
PROM, U37
BLOCK 0
24C04 or 24C08
BLOCK 1
24C04 or 24C08
BLOCK 2
24C08 only
BLOCK 3
24C08 only
READ
0xA9 0xAB 0xAD 0xAF
WRITE
0xA8 0xAA 0xAC 0xAE