Revision 1.6
-16-
02/28/2000
4.3 MCU FUNCTION REGISTERS
Table 4-2 MCU Function Register Summary
Address
Name
Function
00h
INDR
Addressing this location will use the content of INDAR to address data
memory (not a physical address)
01h
TIMER
Timer register
02h
PCL
Program Counter’s low byte
03h
STATUS
Status register
04h
INDAR
Indirect address register
05h
Reserved
06h
PORT1
Port 1 data register
0Ah
PCHBUF
Write buffer of Program Counter’s bit 11-8
0Bh
INTEN
Interrupt enable register
80h
INDR
Addressing this location will use the content of INDAR to address data
memory (not a physical address)
81h
PSCON
Prescaler control register
82h
PCL
Program Counter’s low byte
83h
STATUS
Status register
84h
INDAR
Indirect address register
85h
Reserved
86h
PORT1CON
Port 1 direction control register
8Ah
PCHBUF
Write buffer of Program Counter’s bit 12-8
8Bh
INTEN
Interrupt enable register
INDR (Address 00h/80h)
INDR is not a physical register. Addressing INDR register will cause indirect addressing. Any instruction using the
INDF register actually accesses the register pointed by the INDAR register. The indirect addressing method only can
be used for general purpose registers.
TIMER (Address 01h, Timer register)
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
TIMER7
TIMER6
TIMER5
TIMER4
TIMER3
TIMER2
TIMER1
TIMER0
The timer starts to count up after power on reset. The TMROF bit at INTEN register will be set when the TIMER
register overflows from FFh to 00h. If both TMROEN and GIE bits at INTEN register are set, an interrupt will be
generated when TIMER register overflows.
Value on POR: “0 0 0 0 0 0 0 0”
PCL (Address 02h/82h, Program Counter’s low byte)
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
PCL7
PCL6
PCL5
PCL4
PCL3
PCL2
PCL1
PCL0
The Program Counter (PC) is 12-bits wide. The low byte comes from the PCL register, which is a readable and
writable register. The high byte is not directly readable or writable and comes from PCHBUF. The GL602USB has a 8
level deep x 11-bit wide hardware stake. The stake space is not part of either program or data space and the stack
pointer is not readable or writable. The PC is pushed onto the stack when a CALL instruction is executed or an
interrupt causes a branch. The stack is poped in the event of a RETIA, RETI or a RET instruction execution. PCHBUF
is not affected by a push or pop operation.
Because branch address gotten from stack or direct from instruction is only 11 bits long, the highest bit will be loaded
to PC from PCHBUF when branch instruction is executed.
When write to PCL command executed, all 4 bits of PCHBUF will be loaded to PC because PCL is only a 8 bits
register.
Value on POR: “0 0 0 0 0 0 0 0”
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